Tekton Pipelines relies on its VerificationPolicy to validate resource source strings against patterns defined in spec.resources[].pattern using Go's regexp.MatchString. Because regexp.MatchString returns true when a pattern appears anywhere in the string, unanchored patterns can be bypassed by attacker‑controlled source strings that contain the trusted pattern as a substring. This flaw allows an unintended policy match, causing the pipeline to be verified under an incorrect set of keys or verification modes. The result is that an attacker may gain unauthorized control over the CI/CD workflow by having a resource accepted with the wrong credentials.

This vulnerability affects Tekton Pipelines versions from 0.43.0 up to, but not including, the fixed releases 1.0.2, 1.3.4, 1.6.2, 1.9.3, and 1.11.1. Any cluster running a version older than those fixes and relying on VerificationPolicies for resource validation is impacted.

The CVSS score of 6.5 indicates medium severity. The EPSS score of < 1% indicates a very low exploitation probability, suggesting that the likelihood of attack is low. The vulnerability is not listed in the CISA KEV catalog. The likely attack vector involves an attacker who can supply or influence pipeline resource definitions, inserting a source string that contains the trusted pattern as a substring. By doing so, the attacker can cause an unintended policy match and alter the verification mode or keys applied to the pipeline. The exploitation requires the ability to modify or author a resource within the cluster, which may be achievable through privileged user or compromised CI tooling.