CVE-2026-58053: Gitea act_runner - Container Hardening Bypass via Workflow Container Options

Synopsis

A container hardening bypass exists in Gitea act_runner (through act 0.262.0) with the Docker backend. A remote attacker with a low-privilege account who can trigger a workflow can pass arbitrary container options such as --pid=host and --cap-add through the workflow file's container.options string, which act_runner merges into the Docker HostConfig without sanitization. Successful exploitation lets the attacker escape the job container and gain root-level access on the underlying runner host. HarborGuard is tracking this advisory and will make a patched-image rebuild available the moment upstream publishes a fix.

HarborGuard Coverage

Exploit Conditions

• Network reachabilityRequired

  The attacker triggers the vulnerability by submitting a crafted workflow over the network to the Gitea instance backing the runner, so the service must be reachable over the network.

• AuthenticationRequired

  The attacker must hold at least a low-privilege Gitea account with permission to submit or trigger workflows on a Docker-backed runner.

• Victim interactionNot required

  No victim interaction is needed; the attacker submits the malicious workflow file and the runner processes it automatically.

• Attack complexityDetail

  Exploitation is reliable and condition-free: no race conditions or special environmental layout is required beyond having workflow submission access.

Blast Radius

• Reads any file on the runner host filesystem, including secrets, tokens, and credentials mounted or stored on the host.
• Writes to or modifies the runner host filesystem, enabling persistence mechanisms such as backdoors or modified binaries.
• Crashes or disrupts the runner host process tree by operating within the host PID namespace with root privileges.
• Pivots laterally to other workloads or infrastructure reachable from the host, since the attacker operates as root outside any container boundary.