GHSA-x34h-54cw-9825
HIGHact: actions/cache server allows malicious cache injection
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
github.com/nektos/actReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
act's built-in actions/cache server listens to connections on all interfaces and allows anyone who can connect to it — including someone anywhere on the internet — to create caches with arbitrary keys and retrieve all existing caches. If one can predict which cache keys will be used by local actions, one can create malicious caches containing whatever files one pleases, most likely allowing arbitrary remote code execution within the Docker container.
Discovery
Discovered while discussing forgejo/runner#294.
Proposed Mitigation
It was discussed to append a secret to ACTIONS_CACHE_URL to retain compatibility with GitHub's cache action and still allow authorization. Forgejo is considering also encoding which repo is currently being run in CI into the secret in the URL to prevent unrelated repos using the same (probably global) runner from seeing each other's caches.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/nektos/act | all versions | 0.2.86 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/nektos/act. 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 github.com/nektos/act to 0.2.86 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-x34h-54cw-9825 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-x34h-54cw-9825 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-x34h-54cw-9825. 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-x34h-54cw-9825 in your dependencies?
O3 detects GHSA-x34h-54cw-9825 across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.