Executive Summary

CVE-2026-50141 is a vulnerability in Woodpecker CI's gRPC layer that allows any authenticated agent to impersonate any other agent on the same server. This is done by injecting a forged `agent_id` value into outgoing gRPC metadata. Although the server verifies the JWT token, it incorrectly discards the verified agent identity and instead uses the client-supplied `agent_id`, enabling unauthorized impersonation.

This flaw affects versions 3.0.0 up to 3.14.0 of Woodpecker CI and stems from improper authentication and authorization handling in the server's gRPC communication. The issue was fixed in version 3.14.1 by ensuring the `agent_id` is correctly extracted and stored in the context during gRPC communication, preventing spoofing.

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Impact Analysis

This vulnerability allows an authenticated agent to impersonate other agents on the same Woodpecker CI server, including system agents. This impersonation can lead to unauthorized access to secrets, modification of pipelines, and execution of unauthorized actions across different organizations hosted on the server.

The most severe impact includes gaining access to all queued tasks and their secrets by impersonating a system agent, which can compromise the integrity and confidentiality of the CI/CD environment.

A workaround involves disabling organizational agents and deleting existing ones until the system is patched to version 3.14.1 or later.

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Detection Guidance

The vulnerability involves an authenticated agent injecting a forged `agent_id` into gRPC metadata to impersonate other agents. Detection would involve monitoring gRPC metadata for suspicious or unexpected `agent_id` values that do not match the verified JWT token identities.

Since the issue is related to gRPC metadata manipulation, you can inspect gRPC traffic logs or enable detailed logging on the Woodpecker CI server to identify discrepancies between the JWT-verified agent identity and the client-supplied `agent_id`.

No specific commands are provided in the available resources, but general approaches include:

• Enable verbose logging on the Woodpecker CI server to capture gRPC metadata exchanges.
• Use network packet capture tools (e.g., tcpdump, Wireshark) to filter and analyze gRPC traffic for forged `agent_id` metadata.
• Audit authentication logs to detect agents performing actions on behalf of other agents.

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Mitigation Strategies

The primary mitigation is to upgrade Woodpecker CI to version 3.14.1 or later, where the vulnerability has been patched.

As a workaround before upgrading, you can disable organization agents by setting the environment variable `WOODPECKER_DISABLE_USER_AGENT_REGISTRATION=true` and delete existing agents to prevent impersonation.

These steps help prevent unauthorized agent impersonation by removing the ability for agents to register or reuse forged `agent_id` values.

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Compliance Impact

The vulnerability in Woodpecker CI allows authenticated agents to impersonate other agents on the same server, enabling unauthorized access to secrets, modification of pipelines, and actions across organizations. This impersonation flaw can lead to unauthorized data access and potential data breaches.

Such unauthorized access and potential data exposure could negatively impact compliance with common standards and regulations like GDPR and HIPAA, which require strict controls on data access, authentication, and authorization to protect sensitive information.

By allowing authentication bypass and authorization bypass through spoofing, this vulnerability undermines the security controls necessary to meet these regulatory requirements.

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