CVE: CVE-2026-58053 | CVSS 3.1: 9.9 (CRITICAL) | CWE: CWE-269 Improper Privilege Management | Vendor: Gitea | Product: act_runner (CI/CD runner) with Docker backend through act 0.262.0
What Is the Vulnerability
Gitea act_runner is the CI/CD pipeline execution engine for Gitea — a popular self-hosted Git platform. The Docker backend for act_runner passes a workflow’s container.options string directly to the Docker job container’s HostConfig without sanitization. When the runner is configured with privileged: false, only the Privileged flag is explicitly forced off — all other container options from the workflow definition are merged into the HostConfig unchanged.
An attacker who can submit or modify a CI/CD workflow can inject arbitrary Docker HostConfig options through the container.options field. The attack surface includes:
- –pid=host — access the host process namespace, see all host processes
- –cap-add=SYS_ADMIN — near-root Linux capabilities enabling container escape
- –cap-add=SYS_PTRACE — process tracing and code injection
- –security-opt flags — disable seccomp, AppArmor, and SELinux protections
- –device=/dev/… — mount host devices into the container
- –volume=/:/host — mount the host root filesystem
The runner’s privileged: false setting is completely bypassed because only that single flag is explicitly forced off — every other dangerous option passes through the merge. The result is container escape to the underlying CI/CD host, where the attacker gains access to build secrets, deployment keys, source code, and the entire CI/CD infrastructure.
This is particularly dangerous for public Gitea instances where anyone can submit a pull request with a malicious workflow. Even on private instances, any user with workflow write access (which is the standard permission for contributors) can exploit this.
Versions Affected
- Gitea act_runner with Docker backend — through act 0.262.0
- All configurations where the runner is set to
privileged: falseare affected — the bypass works regardless of this setting - Both self-hosted Gitea instances and Gitea.com cloud runners (if using act_runner with Docker backend)
Exploited?
Proof-of-concept exploit published. No confirmed active exploitation in the wild yet, but the PoC is publicly available at the Exploitarium repository. Given that CI/CD runners are high-value targets and the exploit requires only workflow write access (the standard permission for contributors), active exploitation is likely imminent. Public repositories are at highest risk — anyone can submit a pull request.
Fix
Upgrade act_runner to the patched version. The fix ensures that container.options are sanitized and dangerous HostConfig flags are stripped before being passed to the Docker backend, regardless of the privileged setting.
- Primary fix: Upgrade Gitea act_runner to the latest patched version
- Workaround (immediate): Restrict workflow execution to trusted contributors only. For public repositories, implement workflow approval gates that require manual review before CI/CD execution.
- Alternative backend: Consider using the Kubernetes backend instead of Docker if available, though verify it is not similarly affected.
Recommendations
- Patch act_runner immediately — CVSS 9.9 with public PoC demands urgent action.
- Rotate all CI/CD secrets — if any runner has been compromised, all secrets accessible to it (deployment keys, API tokens, registry credentials, signing keys) should be considered exposed and rotated.
- Audit runner hosts — check CI/CD runner hosts for unexpected processes, containers, or file modifications that could indicate prior compromise.
- Review workflow definitions — audit existing workflow files for suspicious
container.optionsconfigurations, particularly flags like –pid, –cap-add, –security-opt, –device, and –volume. - Implement workflow approval gates — for public repositories or repositories with external contributors, require manual approval before workflows execute.
- Network segment CI/CD runners — runners should not have network access to production environments beyond what is strictly required.
References
Part of the Vulnerability Intelligence series on threat-modeling.com. CVSS 9.9 critical — public PoC available. CI/CD runner compromise exposes secrets, source code, and deployment pipelines. See the June 28, 2026 Vulnerability Intelligence Report for broader context.
