CVE-2026-6272: Kuksa.val Authorization Bypass Vulnerability

CVE-2026-6272 Overview

CVE-2026-6272 is an authorization bypass vulnerability in the Eclipse KUKSA databroker that allows clients with read-only JWT scopes to register as signal providers through the production kuksa.val.v2 OpenProviderStream API. By exploiting this flaw, an attacker can send ProvideSignalRequest messages and inject forged vehicle signal data that other clients will receive as legitimate information.

The vulnerability enables a complete bypass of the intended authorization model, where read-only tokens should not be permitted to write or provide signal data. An attacker exploiting this vulnerability can compromise the integrity of vehicle telemetry data across the entire KUKSA ecosystem.

Critical Impact

Attackers with minimal read-only credentials can inject forged vehicle signal data into the KUKSA databroker, potentially affecting safety-critical automotive systems relying on accurate telemetry.

Affected Products

• Eclipse KUKSA Databroker (kuksa.val.v2 gRPC API)
• Systems utilizing the OpenProviderStream API endpoint
• Vehicle telemetry infrastructure dependent on KUKSA signal integrity

Discovery Timeline

• 2026-04-24 - CVE CVE-2026-6272 published to NVD
• 2026-04-24 - Last updated in NVD database

Technical Details for CVE-2026-6272

Vulnerability Analysis

This vulnerability is classified under CWE-306 (Missing Authentication for Critical Function), indicating that the kuksa.val.v2 gRPC API fails to properly enforce authorization checks when processing ProvideSignalRequest messages through the OpenProviderStream endpoint. The core issue stems from the API accepting provider registration requests from clients regardless of their JWT scope permissions.

In a properly secured implementation, only clients holding write or provider-level JWT scopes should be able to register as signal providers. However, the vulnerable implementation allows any authenticated client—even those with explicitly restricted read-only scopes—to establish a provider stream and inject arbitrary signal values.

The attack surface is network-accessible, requiring low privilege (any valid authentication token) and no user interaction. The impact is severe, affecting the integrity and availability of signal data across the system while potentially propagating malicious data to downstream safety-critical components.

Root Cause

The root cause is the absence of proper authorization validation in the OpenProviderStream API handler. When a client sends a ProvideSignalRequest, the server fails to verify that the client's JWT token includes the necessary write or provider scope. This missing authorization check allows the request to proceed regardless of the token's actual permissions, enabling privilege escalation from read-only to write capabilities.

Attack Vector

The attack follows a specific sequence that exploits the authorization gap:

1. An attacker obtains any valid JWT token with only read scope credentials
2. The attacker establishes a connection to the production gRPC API endpoint (kuksa.val.v2)
3. Using the OpenProviderStream API, the attacker initiates a bidirectional streaming connection
4. The attacker sends a ProvideSignalRequest message specifying a target vehicle signal ID
5. When the broker receives GetProviderValueRequest for that signal, it forwards the request to the attacker
6. The attacker responds with a crafted GetProviderValueResponse containing malicious or forged data
7. Other legitimate clients calling GetValue or GetValues for that signal receive the attacker-controlled data

This attack effectively hijacks signal delivery, allowing the attacker to impersonate legitimate data providers and inject false telemetry values into the vehicle data stream.

Detection Methods for CVE-2026-6272

Indicators of Compromise

• Unexpected OpenProviderStream connections from clients with read-only JWT scopes
• Multiple signal provider registrations from the same client token
• Signal value discrepancies or anomalies compared to expected sensor data patterns
• Authentication logs showing read-scope tokens accessing provider-level API endpoints

Detection Strategies

• Implement server-side logging of all ProvideSignalRequest messages with associated JWT scope information
• Monitor gRPC connection patterns for unusual provider stream establishments
• Deploy anomaly detection on signal values to identify data injection attempts
• Audit JWT token usage patterns to detect scope boundary violations

Monitoring Recommendations

• Enable comprehensive gRPC API request logging with JWT scope extraction
• Configure alerts for any OpenProviderStream API calls from non-provider tokens
• Implement real-time signal value integrity monitoring for critical vehicle telemetry
• Establish baseline behavioral patterns for legitimate provider clients to detect impersonation

How to Mitigate CVE-2026-6272

Immediate Actions Required

• Audit all existing JWT tokens and revoke any that have been potentially compromised
• Implement network-level access controls to restrict OpenProviderStream endpoint access
• Review current provider registrations and validate each against authorized client lists
• Deploy temporary authorization middleware to enforce scope checks on provider APIs

Patch Information

Security updates and patches are tracked through the GitLab CVE Assignment Issue. Organizations should monitor this issue for official patch releases from the Eclipse KUKSA project and apply updates as soon as they become available.

Organizations running affected KUKSA deployments should prioritize patch deployment given the high severity rating and the potential impact on vehicle safety systems.

Workarounds

• Implement a reverse proxy or API gateway that validates JWT scopes before forwarding ProvideSignalRequest messages
• Restrict network access to the gRPC API endpoint to only known, trusted provider clients via firewall rules
• Deploy a custom authorization interceptor that enforces write scope requirements for provider stream operations
• Temporarily disable the OpenProviderStream endpoint if not operationally required until patches are available

# Example: Network-level restriction using iptables to limit gRPC access
# Replace TRUSTED_PROVIDER_IP with actual authorized provider IP addresses

# Block all access to KUKSA gRPC port by default
iptables -A INPUT -p tcp --dport 55555 -j DROP

# Allow only trusted provider clients
iptables -I INPUT -p tcp --dport 55555 -s TRUSTED_PROVIDER_IP -j ACCEPT