CVE-2025-68620: Critical Authentication Bypass in Signal K Server – Risks, Impact & Mitigation

Executive Summary

CVE-2025-68620 represents a critical authentication bypass vulnerability affecting Signal K Server, the central hub application deployed across marine vessel networks worldwide. This vulnerability enables unauthenticated attackers to steal JSON Web Tokens (JWTs) through a chained exploitation of two design flaws: unauthenticated WebSocket event enumeration and unauthenticated REST API token polling.

The severity of this issue cannot be overstated for maritime operations. Successful exploitation grants attackers complete takeover of legitimate device credentials, enabling unauthorized access to vessel systems without any prior authentication. For operators running versions prior to 2.19.0, immediate action is required.

What is CVE-2025-68620?

Vulnerability Overview and Affected Product

CVE-2025-68620 is a critical-severity authentication bypass vulnerability discovered in Signal K Server, an open-source application that serves as the central data hub for marine vessel networks. Signal K Server processes instrument data, manages device access, and coordinates communication between connected maritime systems.

The vulnerability stems from insufficient authorization controls on two key endpoints:

1. WebSocket streaming endpoint (/signalk/v1/stream)
2. REST API access request endpoint (/signalk/v1/access/requests/:id)

When these endpoints are chained together, attackers can extract valid JWT authentication tokens without providing any credentials, effectively bypassing the entire authentication mechanism.

Why This is Critical for Marine Environments

Marine vessels depend on Signal K Server for real-time coordination of critical systems including navigation, propulsion, electrical management, and safety monitoring. A compromised Signal K Server grants attackers control over:

• Navigation and autopilot systems
• Engine and propulsion controls
• Electrical distribution and power management
• Safety and alarm systems
• Vessel monitoring and telemetry data

Unlike traditional IT environments, maritime systems operate in isolated networks where physical access to the vessel is required for recovery. Remote compromise of Signal K Server could result in loss of vessel control, safety hazards, and operational disruption at sea.

Attack Surface and Prerequisites

The vulnerability requires only two prerequisites:

1. Network access to the Signal K Server (typically on the vessel’s internal network)
2. allow_readonly setting enabled in the server configuration (a common default for permitting read-only access to vessel data)

No authentication credentials are needed. No special tools are required beyond basic HTTP and WebSocket clients. The attack can be fully automated and executed at scale against multiple vessels.

Affected Versions and Products

Signal K Server Versions at Risk

Vulnerable: All versions prior to 2.19.0
Patched: Version 2.19.0 and later

The vulnerability affects the entire Signal K Server product line across all deployment environments. There are no partial mitigations within vulnerable versions—the flaw is fundamental to the authorization architecture.

Patched Version Availability

Signal K Server 2.19.0 was released with comprehensive fixes addressing both attack vectors:

• Authorization checks added to the startServerEvents WebSocket function
• Access request endpoint secured to prevent unauthenticated token retrieval
• Configuration validation to prevent unsafe defaults

Deployment Scope in Marine Systems

Signal K Server is deployed across:

• Commercial vessels (cargo ships, tankers, container vessels)
• Passenger ships (cruise lines, ferries)
• Fishing vessels (commercial and industrial fleets)
• Superyachts and luxury vessels
• Naval vessels (some maritime nations)
• Offshore platforms (oil and gas operations)
• Research vessels and oceanographic platforms

Estimates suggest thousands of vessels worldwide operate Signal K Server, with many still running vulnerable versions due to the complexity of maritime software update procedures.

Technical Breakdown of the Vulnerability

Unauthenticated WebSocket Event Enumeration Flaw

The Signal K Server WebSocket endpoint accepts a query parameter serverevents=all that instructs the server to stream all cached server events to the connecting client. This feature is intended for administrative monitoring and debugging.

The vulnerability:

When a client connects with serverevents=all, the server invokes the startServerEvents function, which iterates through app.lastServerEvents and transmits all cached events without performing authorization checks.

When the allow_readonly configuration setting is enabled (which permits unauthenticated users read-only access), the server treats unauthenticated WebSocket connections as readonly users and allows them to connect.

Exposed data includes:

• ACCESS_REQUEST event objects containing:
• Unique request IDs
• Client device identifiers
• Request descriptions
• Requested permission scopes
• Client IP addresses
• Request timestamps

An attacker can passively monitor this stream to identify legitimate access requests from authorized devices, then target those specific requests for token theft.

Unauthenticated REST API Token Polling Weakness

The REST endpoint /signalk/v1/access/requests/:id is designed to allow clients to check the status of their pending access requests. This endpoint uses the queryRequest function to return request state information.

The vulnerability:

This endpoint relies on readonly authorization checks, meaning unauthenticated users can query it when allow_readonly is enabled. More critically, once an administrator approves a pending access request, the endpoint response includes the newly issued JWT token in plaintext.

An attacker can continuously poll this endpoint for request IDs obtained from the WebSocket stream. When an administrator approves a request, the attacker’s next poll retrieves the valid JWT token.

Example vulnerable response:

{
  "id": "request-12345",
  "clientId": "vessel-nav-system",
  "status": "APPROVED",
  "token": "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9...",
  "permissions": ["read", "write"]
}

How the Two Flaws Chain Together

The vulnerability’s true power emerges from chaining these two weaknesses:

Attack sequence:

1. Attacker connects to WebSocket with serverevents=all parameter
2. Server streams all cached ACCESS_REQUEST events to attacker
3. Attacker extracts request IDs from legitimate device requests
4. Attacker begins polling /signalk/v1/access/requests/:id for each request ID
5. When vessel administrator approves a legitimate device’s request, the JWT is issued
6. Attacker’s polling request retrieves the plaintext JWT token
7. Attacker uses stolen JWT to authenticate as the legitimate device
8. Full access to vessel systems is achieved

The attack is passive from the attacker’s perspective—they simply monitor and wait for legitimate administrative actions, then intercept the resulting credentials.

Why allow_readonly Setting Enables Exploitation

The allow_readonly configuration setting is designed to permit unauthenticated users to read vessel data (navigation, engine status, environmental conditions) without requiring authentication. This is useful for:

• Public vessel tracking displays
• Crew information systems
• Guest network access
• Third-party monitoring integrations

However, this setting inadvertently grants unauthenticated access to the access request management endpoints, which should never be exposed without authentication. The vulnerability exists because the developers assumed readonly access would only expose data, not authentication infrastructure.

Attack Paths and Real-World Scenarios

Self-Generated Access Request Exploitation

In this attack path, the attacker creates their own fraudulent access request and waits for administrative approval:

Step-by-step execution:

1. Request creation: Attacker sends a crafted access request to the Signal K Server, potentially using IP spoofing or social engineering to make the request appear legitimate (e.g., “New navigation system installation”)

2. Request ID generation: The server generates a unique request ID and stores it in app.lastServerEvents

3. Continuous polling: Attacker begins polling /signalk/v1/access/requests/:id with the known request ID, checking status repeatedly

4. Administrator approval: A vessel administrator reviews the request and approves it, believing it to be a legitimate system upgrade or maintenance request

5. Token interception: Attacker’s next polling request receives the plaintext JWT token in the response

6. Authentication bypass: Attacker uses the stolen JWT to authenticate to the Signal K Server as an approved device

7. System compromise: With valid credentials, attacker can read all vessel data and potentially execute commands depending on the approved permissions

Real-world scenario:

A vessel receives a maintenance notification about a “navigation system firmware update.” The vessel’s IT staff approves the access request without realizing it originated from an attacker. The attacker, monitoring the request status, intercepts the issued JWT and gains full access to the vessel’s navigation systems.

Passive Eavesdropping and Credential Hijacking

This attack path is more sophisticated—the attacker hijacks legitimate device credentials rather than creating fraudulent requests:

Step-by-step execution:

1. WebSocket monitoring: Attacker connects to the Signal K WebSocket stream with serverevents=all and begins monitoring incoming ACCESS_REQUEST events

2. Legitimate request identification: Attacker observes legitimate devices requesting access (e.g., “Ballast Management System,” “Weather Station Integration,” “Engine Monitoring Unit”)

3. Request ID extraction: For each legitimate request, the attacker extracts and records the request ID

4. Targeted polling: Attacker begins polling /signalk/v1/access/requests/:id for the legitimate request IDs

5. Administrative approval: The vessel’s administrator approves the legitimate device’s access request, unaware that an attacker is monitoring

6. Token hijacking: Attacker’s polling request retrieves the JWT token intended for the legitimate device

7. Session takeover: Attacker uses the stolen JWT to authenticate as the legitimate device

8. Impersonation: From the server’s perspective, the attacker is now the legitimate device, with all associated permissions

Real-world scenario:

A vessel’s ballast management system requests access to the Signal K Server. The administrator approves the request. Simultaneously, an attacker monitoring the WebSocket stream intercepts the issued JWT. The attacker can now send commands to the ballast system, potentially causing operational hazards or safety issues.

Automation and Scalability of Attacks

The vulnerability is trivial to automate, enabling large-scale attacks:

Automated attack framework:

1. Scan for Signal K Servers on target networks
2. For each server:
   a. Connect to WebSocket with serverevents=all
   b. Parse incoming ACCESS_REQUEST events
   c. Extract all request IDs
   d. Begin polling /signalk/v1/access/requests/:id for each ID
   e. Store retrieved JWTs in database
   f. Monitor for new requests and repeat
3. Maintain database of valid JWTs for each vessel
4. Execute commands using stolen credentials

An attacker could target hundreds of vessels simultaneously with minimal computational overhead. The attack requires no interaction with the target—it’s entirely passive until the attacker chooses to use stolen credentials.

Threat Assessment and Impact

Authentication Bypass Consequences

The fundamental consequence of CVE-2025-68620 is complete authentication bypass. The vulnerability eliminates the authentication layer entirely, allowing attackers to operate as legitimate, approved devices without possessing any credentials.

Authentication bypass implications:

• All access controls dependent on JWT validation are circumvented
• Audit logs show legitimate device identities (not the attacker)
• Intrusion detection systems may not flag the activity as anomalous
• The attacker operates with the same permissions as the hijacked device

Session Takeover and Device Control Risks

Once an attacker obtains a valid JWT, they can impersonate the associated device and execute any operations permitted by that device’s access scope.

Potential device control scenarios:

Confidentiality and Integrity Loss

Confidentiality impact:

• All vessel operational data becomes accessible to the attacker
• Navigation routes, schedules, and cargo information exposed
• Crew information and vessel security details compromised
• Competitive intelligence and business information disclosed

Integrity impact:

• Attacker can modify vessel data and system configurations
• False sensor readings can be injected into monitoring systems
• Historical data can be altered to cover attack tracks
• System configurations can be changed to enable persistent access

Operational Impact on Vessel Systems

The operational consequences of a compromised Signal K Server extend beyond individual system control:

Cascading failures:

1. Navigation disruption: Attacker alters course or disables navigation systems
2. Propulsion loss: Engine systems are shut down or throttled
3. Safety system failure: Emergency systems are disabled or suppressed
4. Communication blackout: Radio and satellite systems are disabled
5. Crew safety: Crew cannot communicate distress or request assistance

Business impact:

• Vessel operational downtime and schedule disruption
• Cargo delivery delays and contract penalties
• Reputation damage and loss of customer confidence
• Regulatory fines and compliance violations
• Insurance claim complications

Detection and Monitoring Strategies

WebSocket Traffic Indicators

Monitor WebSocket connections for suspicious patterns indicating exploitation attempts:

Detection signatures:

1. Suspicious connection parameters:

   WebSocket connection with serverevents=all parameter
   from unauthenticated or unknown client

1. Rapid event streaming:

• Baseline: Legitimate monitoring generates 10-50 events per minute
• Suspicious: 100+ events per minute from single connection
• Indicator: Attacker attempting to capture all historical events

1. Unusual client identifiers:

• Monitor for WebSocket connections with generic or suspicious User-Agent headers
• Flag connections from non-standard maritime device identifiers
• Alert on connections from external networks

1. Connection duration patterns:

• Baseline: Monitoring connections typically last 5-30 minutes
• Suspicious: Persistent connections lasting hours or days
• Indicator: Attacker maintaining continuous event stream monitoring

Log analysis query example:

websocket_connections 
  where query_parameters contains "serverevents=all" 
  and authenticated = false 
  and duration > 3600 seconds

REST API Polling Patterns to Flag

The REST API endpoint /signalk/v1/access/requests/:id should receive minimal traffic under normal operations. Suspicious patterns indicate exploitation:

Detection signatures:

1. High-frequency polling:

• Baseline: Legitimate clients poll once per request (typically 1-5 requests per day)
• Suspicious: 10+ requests per minute to the same endpoint
• Indicator: Attacker polling for token availability

1. Polling for non-existent requests:

• Monitor for requests to /signalk/v1/access/requests/:id where :id doesn’t exist in the system
• Baseline: Legitimate clients know their request IDs
• Suspicious: Systematic enumeration of request ID space

1. Unauthenticated polling:

• All polling should originate from authenticated sessions
• Baseline: Zero unauthenticated requests
• Suspicious: Any unauthenticated request to this endpoint

1. Polling before request approval:

• Monitor for polling attempts before administrator approval
• Baseline: Polling begins after approval
• Suspicious: Polling begins immediately after request creation

Log analysis query example:

http_requests 
  where path matches "/signalk/v1/access/requests/*" 
  and authenticated = false 
  group by source_ip, request_id 
  having count(*) > 10 in 60 seconds

Log Analysis for Suspicious Access Requests

Examine access request logs for patterns indicating fraudulent or hijacked requests:

Suspicious patterns:

1. Requests from unexpected sources:

• Monitor for access requests originating from external networks
• Flag requests from IP addresses not associated with vessel operations
• Alert on requests from known attack infrastructure

1. Unusual request descriptions:

• Baseline: Requests contain specific device names and purposes
• Suspicious: Generic descriptions (“System Update,” “Maintenance”)
• Indicator: Attacker creating plausible but vague requests

1. Rapid request approval:

• Baseline: Administrators review requests before approval (5-30 minute delay)
• Suspicious: Immediate approval without review
• Indicator: Attacker’s own request being approved by compromised administrator

1. Multiple requests from same source:

• Monitor for repeated access requests from the same IP or device
• Baseline: Devices request access once
• Suspicious: Same device requesting access multiple times
• Indicator: Attacker attempting multiple exploitation paths

1. Requests with escalated permissions:

• Flag requests asking for write or admin permissions
• Baseline: Most requests are read-only
• Suspicious: Requests for elevated permissions from unknown sources

Log analysis query example:

access_requests 
  where status = "APPROVED" 
  and time_to_approval < 300 seconds 
  and source_ip not in (known_vessel_networks)

Network-Level Detection Approaches

Implement network-level monitoring to detect exploitation attempts:

Network detection strategies:

1. WebSocket traffic analysis:

• Monitor for WebSocket connections to Signal K Server from unexpected sources
• Baseline: Connections from vessel internal network and authorized remote systems
• Suspicious: Connections from external networks or unknown devices

1. API request rate limiting:

• Implement rate limiting on /signalk/v1/access/requests/* endpoint
• Baseline: <5 requests per minute per source
• Suspicious: >10 requests per minute triggers alert

1. Geolocation analysis:

• Monitor for API requests originating from geographic locations inconsistent with vessel operations
• Flag requests from known attack infrastructure or suspicious regions

1. Behavioral analysis:

• Establish baseline of normal Signal K Server traffic patterns
• Alert on deviations: unusual request types, timing, or sources
• Machine learning models can identify anomalous patterns

1. Network segmentation monitoring:

• Monitor for attempts to access Signal K Server from outside designated network segments
• Alert on lateral movement attempts from compromised systems

Remediation and Patching

Upgrade to Signal K Server 2.19.0

The primary and most effective remediation is upgrading to Signal K Server version 2.19.0 or later. This version includes comprehensive fixes addressing both vulnerability vectors.

Upgrade procedure:

1. Pre-upgrade planning:

• Schedule upgrade during vessel maintenance window or low-operational-demand period
• Backup current Signal K Server configuration and data
• Document current system state for rollback capability
• Notify crew and dependent systems of planned downtime

1. Backup current installation:

   # Backup configuration
   cp -r /opt/signalk/config /backup/signalk-config-backup
   # Backup data
   cp -r /opt/signalk/data /backup/signalk-data-backup

1. Download and verify version 2.19.0:

• Obtain Signal K Server 2.19.0 from official repository
• Verify package integrity using provided checksums
• Confirm digital signatures if available

1. Stop current Signal K Server:

   systemctl stop signalk

1. Install new version:

   # Extract new version
   tar -xzf signalk-server-2.19.0.tar.gz -C /opt/signalk
   # Install dependencies
   cd /opt/signalk && npm install

1. Verify configuration compatibility:

• Review configuration files for deprecated settings
• Update any settings that changed between versions
• Test configuration in non-production environment first

1. Start upgraded Signal K Server:

   systemctl start signalk

1. Verify functionality:

• Confirm all connected devices can authenticate
• Verify data streaming is functioning correctly
• Check logs for errors or warnings
• Test access request approval workflow

1. Monitor post-upgrade:

• Monitor system logs for 24-48 hours after upgrade
• Verify no unexpected disconnections or errors
• Confirm performance is consistent with pre-upgrade baseline

Upgrade timeline:

• Immediate (within 24 hours): Vessels in high-risk environments or with external network access
• Short-term (within 1 week): All commercial vessels and vessels with crew safety systems
• Medium-term (within 30 days): All remaining vessels

Immediate Temporary Controls

For vessels unable to upgrade immediately, implement temporary controls to reduce exploitation risk:

Temporary control 1: Disable allow_readonly setting

The most effective temporary mitigation is disabling unauthenticated readonly access:

# In Signal K Server configuration (typically config/settings.json)
{
  "security": {
    "allow_readonly": false
  }
}

Impact of disabling allow_readonly:

• Eliminates unauthenticated access to WebSocket stream
• Prevents unauthenticated polling of access request endpoint
• Requires all clients to authenticate before accessing any data
• May break legitimate read-only integrations (public displays, guest networks)

Workaround for legitimate read-only access:

• Create dedicated read-only user accounts for each legitimate read-only client
• Require authentication for all access, even read-only
• Use API tokens with limited scope instead of full server access

Temporary control 2: Firewall rule implementation

Restrict network access to Signal K Server to only authorized devices:

# Allow only internal vessel network
iptables -A INPUT -p tcp --dport 3000 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 3000 -j DROP
# Allow only specific authorized external IPs
iptables -A INPUT -p tcp --dport 3000 -s 203.0.113.50 -j ACCEPT  # Fleet management system
iptables -A INPUT -p tcp --dport 3000 -s 203.0.113.51 -j ACCEPT  # Monitoring service

Firewall rule considerations:

• Identify all legitimate clients that need access
• Document IP addresses or network ranges for each client
• Implement rules at both firewall and application level
• Monitor for legitimate clients unable to connect due to rules

Network Segmentation Strategies

Implement network segmentation to limit the impact of a compromised Signal K Server:

Segmentation approach 1: VLAN isolation

Vessel Network Architecture:
├── Management VLAN (10.0.1.0/24)
│   └── Signal K Server (isolated)
├── Operational VLAN (10.0.2.0/24)
│   ├── Navigation Systems
│   ├── Engine Management
│   └── Ballast Systems
├── Crew VLAN (10.0.3.0/24)
│   ├── Crew WiFi
│   └── Guest Network
└── External VLAN (10.0.4.0/24)
    └── Satellite/Cellular Gateway

Access control rules:

• Operational systems can initiate connections to Signal K Server
• Signal K Server cannot initiate connections to operational systems
• Crew and external networks have no direct access to Signal K Server
• All inter-VLAN traffic is logged and monitored

Segmentation approach 2: Firewall-based access control

Signal K Server Access Rules:
├── Allow: Navigation System → Signal K (read/write)
├── Allow: Engine System → Signal K (read/write)
├── Allow: Ballast System → Signal K (read/write)
├── Allow: Monitoring System → Signal K (read-only)
├── Deny: Signal K → Navigation System
├── Deny: Signal K → Engine System
├── Deny: Signal K → Ballast System
└── Deny: External Networks → Signal K

Configuration Hardening Steps

Implement security hardening in Signal K Server configuration:

Hardening step 1: Disable unnecessary endpoints

# Disable endpoints not required for operations
{
  "endpoints": {
    "websocket": true,
    "rest": true,
    "mqtt": false,
    "signalk-http": false
  }
}

Hardening step 2: Implement strong authentication

# Require strong authentication for all access
{
  "security": {
    "allow_readonly": false,
    "require_authentication": true,
    "jwt_expiration": 3600,
    "password_policy": {
      "min_length": 12,
      "require_uppercase": true,
      "require_numbers": true,
      "require_special": true
    }
  }
}

Hardening step 3: Enable comprehensive logging

# Log all access and authentication events
{
  "logging": {
    "level": "info",
    "log_authentication": true,
    "log_access_requests": true,
    "log_api_calls": true,
    "log_file": "/var/log/signalk/access.log"
  }
}

Hardening step 4: Implement rate limiting

# Prevent brute force and DoS attacks
{
  "rate_limiting": {
    "enabled": true,
    "requests_per_minute": 60,
    "requests_per_hour": 3600,
    "burst_limit": 10
  }
}

Workarounds for Delayed Patching

For vessels unable to upgrade immediately, implement these workarounds to reduce risk:

Disabling allow_readonly Setting

Configuration change:

Edit the Signal K Server configuration file (typically config/settings.json):

{
  "security": {
    "allow_readonly": false
  }
}

Restart Signal K Server:

systemctl restart signalk

Verification:

# Test that unauthenticated access is denied
curl -i http://localhost:3000/signalk/v1/api/
# Should return 401 Unauthorized
# HTTP/1.1 401 Unauthorized

Impact assessment:

Firewall Rule Implementation

Linux firewall rules (iptables):

# Backup current rules
iptables-save > /etc/iptables/rules.v4.backup
# Allow only internal network
iptables -A INPUT -p tcp --dport 3000 -s 192.168.1.0/24 -j ACCEPT
# Allow specific external systems
iptables -A INPUT -p tcp --dport 3000 -s 203.0.113.50 -j ACCEPT  # Fleet management
iptables -A INPUT -p tcp --dport 3000 -s 203.0.113.51 -j ACCEPT  # Monitoring
# Deny all other access
iptables -A INPUT -p tcp --dport 3000 -j DROP
# Save rules
iptables-save > /etc/iptables/rules.v4

Hardware firewall rules:

Rule 1: Allow 192.168.1.0/24 → Signal K Server:3000 (internal network)
Rule 2: Allow 203.0.113.50 → Signal K Server:3000 (fleet management)
Rule 3: Allow 203.0.113.51 → Signal K Server:3000 (monitoring service)
Rule 4: Deny any → Signal K Server:3000 (default deny)

Verification:

# From authorized network
curl -i http://signalk-server:3000/signalk/v1/api/
# Should return 200 OK or 401 (authentication required)
# From unauthorized network
curl -i http://signalk-server:3000/signalk/v1/api/
# Should timeout or return connection refused

Access Restriction Best Practices

Best practice 1: Principle of least privilege

• Grant each device only the minimum permissions required
• Use role-based access control (RBAC) where available
• Regularly audit and revoke unnecessary permissions

Best practice 2: Access request approval workflow

1. Device requests access with specific permissions
2. Request is logged with timestamp and source
3. Administrator reviews request details
4. Administrator approves or denies request
5. Approval/denial is logged
6. Device receives JWT token (if approved)

Best practice 3: Regular credential rotation

• Rotate JWT tokens on a regular schedule (monthly or quarterly)
• Revoke tokens for devices no longer in use
• Implement token expiration (e.g., 24-hour expiration)

Best practice 4: Monitoring and alerting

• Monitor for unusual access patterns
• Alert on failed authentication attempts
• Track all access request approvals
• Log all API calls and data access

Monitoring During Transition Period

Daily monitoring checklist:

• [ ] Review Signal K Server logs for errors or warnings
• [ ] Check for unexpected access requests
• [ ] Verify all legitimate devices can authenticate
• [ ] Monitor for suspicious WebSocket connections
• [ ] Check API request rates for anomalies
• [ ] Review firewall logs for blocked connections
• [ ] Verify no legitimate services are broken

Weekly monitoring tasks:

• [ ] Analyze access patterns for anomalies
• [ ] Review authentication failure logs
• [ ] Audit approved access requests
• [ ] Check for unauthorized network access attempts
• [ ] Verify backup and recovery procedures
• [ ] Test failover systems

Monthly monitoring tasks:

• [ ] Comprehensive security audit
• [ ] Review and update firewall rules
• [ ] Audit user accounts and permissions
• [ ] Test incident response procedures
• [ ] Review vendor security advisories
• [ ] Plan upgrade timeline

Frequently Asked Questions

What is Signal K Server and why is it used?

Signal K Server is an open-source server application that acts as a central data hub on marine vessels. It processes data from various ship systems (navigation, engines, ballast, electrical, etc.) and makes this data available to connected applications and devices.

Why it’s used:

• Data centralization: Consolidates data from multiple ship systems into a single source
• Standardization: Uses the Signal K standard format for marine data
• Integration: Enables third-party applications to access vessel data
• Monitoring: Provides real-time monitoring of vessel systems
• Automation: Enables automated responses to system events
• Remote management: Allows shore-based monitoring and management

Typical deployment:

Signal K Server runs on a dedicated computer or embedded system on the vessel, connected to the vessel’s internal network. It communicates with navigation systems, engine management systems, ballast systems, and other equipment via various protocols (NMEA 0183, NMEA 2000, etc.).

Is authentication required to exploit this vulnerability?

No. This is the critical aspect of CVE-2025-68620. When the allow_readonly setting is enabled (which is common), no authentication is required to exploit the vulnerability.

An attacker needs only:

• Network access to the Signal K Server
• Knowledge of the vulnerable endpoints (which are standard)
• Basic HTTP and WebSocket client capabilities

No credentials, API keys, or authentication tokens are needed to begin the exploitation process.

What sensitive data is exposed through the WebSocket endpoint?

The WebSocket endpoint with serverevents=all parameter exposes all cached server events, including:

From ACCESS_REQUEST events:

• Request IDs (used to poll for tokens)
• Client device identifiers
• Request descriptions
• Requested permission scopes
• Client IP addresses
• Request timestamps
• Request status (pending, approved, denied)

From other server events:

• System status changes
• Configuration modifications
• Error conditions
• Administrative actions

This information is valuable to attackers for:

• Identifying legitimate devices to impersonate
• Understanding vessel system architecture
• Timing attacks to coincide with administrative actions
• Crafting convincing fraudulent requests

Can attackers hijack legitimate device credentials?

Yes. This is one of the two primary attack paths for CVE-2025-68620.

How it works:

1. Attacker monitors WebSocket stream for legitimate device access requests
2. Attacker extracts request IDs from legitimate devices
3. Attacker polls the access request endpoint for those request IDs
4. When administrator approves the legitimate device’s request, the JWT is issued
5. Attacker’s polling request retrieves the JWT before the legitimate device
6. Attacker uses the JWT to impersonate the legitimate device

Impact:

• Attacker operates with the legitimate device’s permissions
• Audit logs show the legitimate device making the requests
• Intrusion detection may not flag the activity as anomalous
• The legitimate device may be unable to connect (JWT already used)

How quickly can this vulnerability be exploited?

Exploitation timeline:

• Reconnaissance: 1-5 minutes (identify Signal K Server and enumerate requests)
• Monitoring: Ongoing (attacker maintains WebSocket connection)
• Token theft: Seconds to minutes (once administrator approves a request)