CVE-2023-25809 is a medium-severity (CVSS 5) CWE-281 vulnerability in github.com/opencontainers/runc. 1 public exploit reference exists, so weaponization risk is real. A fix is available for github.com/opencontainers/runc — see the affected versions and patch details below.
rootless: `/sys/fs/cgroup` is writable when cgroupns isn't unshared in runc
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2023-25809.
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.
How urgent is this, really
CVE-2023-25809 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,636 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
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 affected versions it was found that rootless runc makes /sys/fs/cgroup writable in following conditons: 1. when runc is executed inside the user namespace, and the config.json does not specify the cgroup namespace to be unshared (e.g.., (docker|podman|nerdctl) run --cgroupns=host, with Rootless Docker/Podman/nerdctl) or 2. when runc is executed outside the user namespace, and /sys is mounted with rbind, ro (e.g., runc spec --rootless; this condition is very rare). A container may gain the write access to user-owned cgroup hierarchy /sys/fs/cgroup/user.slice/... on the host . Other users's cgroup hierarchies are not affected. Users are advised to upgrade to version 1.1.5. Users unable to upgrade may unshare the cgroup namespace ((docker|podman|nerdctl) run --cgroupns=private). This is the default behavior of Docker/Podman/nerdctl on cgroup v2 hosts. or add /sys/fs/cgroup to maskedPaths.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/opencontainers/runc | all versions | 1.1.5go get github.com/opencontainers/runc@v1.1.5 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
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, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/opencontainers/runc to 1.1.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-25809 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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2023-25809 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2023-25809. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat Enterprise Linux 8 | container-tools:4.0-8090020230828093056.e7857ab1 | RHSA-2023:6938 |
| Red Hat Enterprise Linux 8 | container-tools:rhel8-8090020230825121312.e7857ab1 | RHSA-2023:6939 |
| Red Hat Enterprise Linux 9 | runc-4:1.1.9-1.el9 | RHSA-2023:6380 |
| Red Hat OpenShift Container Platform 4.13 | openshift4/ose-vsphere-csi-driver-syncer-rhel8:v4.13.0-202304190216.p0.g6f4295b.assembly.stream | RHSA-2023:1326 |
Frequently Asked Questions
Is CVE-2023-25809 in your dependencies?
O3 Security finds CVE-2023-25809 across Go dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.