rootless: /sys/fs/cgroup is writable when cgroupns isn't unshared in runc

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

2.5 · CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:C/C:N/I:N/A:L

EPSS

• CVE-2023-25809: 0.32% estimated exploitation activity in the next 30 days; percentile 24.93 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Impact 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) 2. or, 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. Patches v1.1.5 (planned) Workarounds - Condition 1: Unshare the cgroup namespace ((docker|podman|nerdctl) run --cgroupns=private). This is the default behavior of Docker/Podman/nerdctl on cgroup v2 hosts. - Condition 2 (very rare): add /sys/fs/cgroup to maskedPaths

Published by the source

30 Mar 2023, 20:17 UTC

Last modified by the source

30 Mar 2023, 20:17 UTC

Source last checked

26 Oct 2026, 14:58 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-m8cg-xc2p-r3fc

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# Patch Next advisory brief: CVE-2023-25809

Advisory: rootless: `/sys/fs/cgroup` is writable when cgroupns isn't unshared in runc
IDs: CVE-2023-25809, GHSA-m8cg-xc2p-r3fc
Record: https://patchnext.com/advisories/cve-2023-25809 (revision 1, source checked 26 Oct 2026, 14:58 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Low (CVSS 2.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/opencontainers/runc 1.1.5. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/opencontainers/runc: affected < 1.1.5; fixed in 1.1.5

## Suggested inspection (read-only)
- Go github.com/opencontainers/runc: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/opencontainers/runc.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-m8cg-xc2p-r3fc (GitHub-reviewed advisory GHSA-m8cg-xc2p-r3fc lists affected ranges: Go github.com/opencontainers/runc >=0 <1.1.5)

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