GHSA-mxr3-8whj-j74r
MEDIUMHarden-Runner allows evasion of 'disable-sudo' policy
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Blast Radius
step-security/harden-runnerReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects GitHub Actions packages — download data is not available via public APIs for these ecosystems.
Description
Summary
Harden-Runner includes a policy option disable-sudo to prevent the GitHub Actions runner user from using sudo. This is implemented by removing the runner user from the sudoers file. However, this control can be bypassed as the runner user, being part of the docker group, can interact with the Docker daemon to launch privileged containers or access the host filesystem. This allows the attacker to regain root access or restore the sudoers file, effectively bypassing the restriction.
For an attacker to bypass this control, they would first need the ability to run their malicious code (e.g., by a supply chain attack similar to tj-actions or exploiting a Pwn Request vulnerability)) on the runner. This vulnerability has been fixed in Harden-Runner version v2.12.0.
Impact
An attacker with the ability to run their malicious code on a runner configured with disable-sudo: true can escalate privileges to root using Docker, defeating the intended security control.
Affected Configuration
• Harden-Runner configurations that use disable-sudo: true on GitHub-hosted runners or on ephemeral self-hosted VM-based runners.
• This issue does not apply to Kubernetes-based Actions Runner Controller (ARC) Harden-Runner.
Mitigation / Fix
This vulnerability has been fixed in Harden-Runner version v2.12.0. Users should migrate to the stronger disable-sudo-and-containers policy. This setting:
• Disables sudo access,
• Removes access to dockerd and containerd sockets,
• Uninstalls Docker from the runner entirely, preventing container-based privilege escalation paths.
Additional Improvements
• The disable-sudo option will be deprecated in the future, as it does not sufficiently restrict privilege escalation on its own.
• Harden-Runner now includes detections to alert on attempts to evade the disable-sudo policy.
Credits
Reported by @loresuso and @darryk10. We would like to thank them for collaborating with us to mitigate the vulnerability.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦GitHub Actions | step-security/harden-runner | ≥ 0.12.0&&< 2.12.0 | 2.12.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for step-security/harden-runner. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update step-security/harden-runner to 2.12.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-mxr3-8whj-j74r is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-mxr3-8whj-j74r is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-mxr3-8whj-j74r. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-mxr3-8whj-j74r in your dependencies?
O3 detects GHSA-mxr3-8whj-j74r across GitHub Actions dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.