The vulnerability in Gitea act_runner with Docker backend (act 0.262.0) involves improper privilege management. Specifically, the container.options string from a workflow is merged into the Docker job container's HostConfig. When configured with privileged: false, only the Privileged flag is disabled, but other options such as --pid=host, --cap-add, and --security-opt are preserved. This enables a user able to run workflows on the Docker-backed runner to create containers with host namespaces and broad capabilities, leading to a host root escape despite privileged mode being disabled. The CVSS 3.1 score is 9.9 (critical), reflecting network attack vector, low attack complexity, low privileges required, no user interaction, scope change, and high impact on confidentiality, integrity, and availability. No patch or official remediation is currently documented, and no known exploits in the wild have been reported.

An attacker with the ability to run workflows on a Docker-backed Gitea act_runner can escalate privileges by creating a container with host namespaces and elevated capabilities. This results in a host root escape, compromising the host system's confidentiality, integrity, and availability. The vulnerability bypasses the intended security control of disabling privileged mode, allowing unauthorized root-level access on the host.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is available, restrict workflow execution permissions to trusted users only and avoid running untrusted workflows on Docker-backed runners. Monitor vendor channels for updates and apply patches promptly once released.