CVE-2025-31133
Fix: opencontainers/runc@1a30a8fCVE-2025-31133 is a CWE-61 vulnerability in github.com/opencontainers/runc. O3 Security confirms whether CVE-2025-31133 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
runc container escape via "masked path" abuse due to mount race conditions
Real-World Exposure
github.com/opencontainers/runc🐹github.com/opencontainers/runc🐹github.com/opencontainers/runcReal-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
runc is a CLI tool for spawning and running containers according to the OCI specification. In versions 1.2.7 and below, 1.3.0-rc.1 through 1.3.1, 1.4.0-rc.1 and 1.4.0-rc.2 files, runc would not perform sufficient verification that the source of the bind-mount (i.e., the container's /dev/null) was actually a real /dev/null inode when using the container's /dev/null to mask. This exposes two methods of attack: an arbitrary mount gadget, leading to host information disclosure, host denial of service, container escape, or a bypassing of maskedPaths. This issue is fixed in versions 1.2.8, 1.3.3 and 1.4.0-rc.3.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/opencontainers/runc | all versions | 1.2.8 |
| 🐹Go | github.com/opencontainers/runc | ≥ 1.3.0-rc.1&&< 1.3.3 | 1.3.3 |
| 🐹Go | github.com/opencontainers/runc | ≥ 1.4.0-rc.1&&< 1.4.0-rc.3 | 1.4.0-rc.3 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/opencontainers/runc. 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/opencontainers/runc to 1.2.8 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-31133 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 CVE-2025-31133 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 CVE-2025-31133. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2025-31133 in your dependencies?
O3 detects CVE-2025-31133 across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.