In woodpecker versions before 3.15.0, the ApprovalAllowedUsers bypass list is matched against pipeline.Author, which for the GitLab forge driver is derived from the git commit author name in the webhook payload. Since this author name is attacker-controlled and not verified by GitLab, an attacker opening a merge request from a fork can spoof an approved user by setting the commit author name accordingly. This causes the needsApproval check to return false, allowing the pipeline to run without the required approval. This vulnerability breaks the fork-approval security boundary, enabling execution of attacker-controlled pipeline steps on a Woodpecker agent and potential exfiltration of CI secrets. Other forge drivers are unaffected because they use forge-validated sender identities.

An attacker who can open a merge request from a fork in GitLab can bypass the approval mechanism in Woodpecker CI, leading to unauthorized execution of pipeline steps. This can result in execution of arbitrary code on Woodpecker agents and potential exfiltration of sensitive CI secrets. The vulnerability affects confidentiality, integrity, and availability of the CI environment. Other forge drivers are not impacted.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is available, users should consider restricting merge request permissions from forks or disabling the affected GitLab forge driver integration to prevent exploitation. Monitor vendor channels for updates and apply patches promptly once released.