Tekton Pipelines Git Resolver API Token Leak via ServerURL Manipulation (CVE-2026-40161)

Tekton Pipelines, a Kubernetes-style resource for declaring CI/CD pipelines, contains a vulnerability (CVE-2026-40161) in its git resolver component. Specifically, versions 1.0.0 to 1.10.0 are affected. When operating in API mode, the resolver inadvertently sends the system-configured Git API token (e.g., GitHub PAT, GitLab token) to a server specified by the user if the token parameter is omitted. This allows an attacker with TaskRun or PipelineRun creation privileges to exfiltrate the shared API token by directing the serverURL to an attacker-controlled endpoint. The vulnerability allows for the potential compromise of CI/CD pipelines and related infrastructure.

Attack Chain

1. An attacker gains access to a Kubernetes tenant with permissions to create TaskRun or PipelineRun resources within Tekton Pipelines.
2. The attacker crafts a malicious TaskRun or PipelineRun configuration.
3. The configuration leverages the Tekton Pipelines git resolver in API mode.
4. The attacker omits the token parameter in the git resolver configuration, forcing the system to use the system-configured Git API token.
5. The attacker sets the serverURL parameter to an attacker-controlled endpoint.
6. Tekton Pipelines, upon execution of the TaskRun or PipelineRun, sends the system-configured Git API token to the attacker-controlled serverURL.
7. The attacker’s server logs and captures the leaked Git API token.
8. The attacker uses the exfiltrated token to access and potentially compromise Git repositories or other services authenticated by the token.

Impact

Successful exploitation of CVE-2026-40161 allows an attacker to steal the system-configured Git API token used by Tekton Pipelines. This could lead to unauthorized access to Git repositories, the modification of code, and the potential compromise of the entire CI/CD pipeline. Given Tekton’s widespread adoption, a successful attack could affect numerous organizations using the vulnerable versions.

Recommendation

• Upgrade Tekton Pipelines to a version greater than 1.10.0 to remediate CVE-2026-40161.
• Implement strict access controls within the Kubernetes cluster to limit TaskRun and PipelineRun creation privileges to authorized users only.
• Monitor network traffic originating from Tekton Pipeline pods for connections to unusual or untrusted serverURL destinations as specified in CVE-2026-40161. Create a network connection rule for this.
• Review Tekton Pipeline configurations for suspicious serverURL parameters using a file monitoring rule.