CVE-2025-52881

runc is a CLI tool for spawning and running containers according to the OCI specification. In versions 1.2.7, 1.3.2 and 1.4.0-rc.2, an attacker can trick runc into misdirecting writes to /proc to other procfs files through the use of a racing container with shared mounts (we have also verified this attack is possible to exploit using a standard Dockerfile with docker buildx build as that also permits triggering parallel execution of containers with custom shared mounts configured). This redirect could be through symbolic links in a tmpfs or theoretically other methods such as regular bind-mounts. While similar, the mitigation applied for the related CVE, CVE-2019-19921, was fairly limited and effectively only caused runc to verify that when LSM labels are written they are actually procfs files. This issue is fixed in versions 1.2.8, 1.3.3, and 1.4.0-rc.3.

Weakness

The product, when opening a file or directory, does not sufficiently account for when the file is a symbolic link that resolves to a target outside of the intended control sphere. This could allow an attacker to cause the product to operate on unauthorized files.

Affected Software

Potential Mitigations

• Follow the principle of least privilege when assigning access rights to entities in a software system.
• Denying access to a file can prevent an attacker from replacing that file with a link to a sensitive file. Ensure good compartmentalization in the system to provide protected areas that can be trusted.

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/27.html

References

• http://github.com/opencontainers/runc/commit/a41366e74080fa9f26a2cd3544e2801449697322
• http://github.com/opencontainers/runc/commit/fdcc9d3cad2f85954a241ccb910a61aaa1ef47f3
• https://github.com/opencontainers/runc/blob/v1.4.0-rc.2/RELEASES.md
• https://github.com/opencontainers/runc/commit/3f925525b44d247e390e529e772a0dc0c0bc3557
• https://github.com/opencontainers/runc/commit/435cc81be6b79cdec73b4002c0dae549b2f6ae6d
• https://github.com/opencontainers/runc/commit/44a0fcf685db051c80b8c269812bb177f5802c58
• https://github.com/opencontainers/runc/commit/4b37cd93f86e72feac866442988b549b5b7bf3e6
• https://github.com/opencontainers/runc/commit/6fc191449109ea14bb7d61238f24a33fe08c651f
• https://github.com/opencontainers/runc/commit/77889b56db939c323d29d1130f28f9aea2edb544
• https://github.com/opencontainers/runc/commit/77d217c7c3775d8ca5af89e477e81568ef4572db
• https://github.com/opencontainers/runc/commit/b3dd1bc562ed9996d1a0f249e056c16624046d28
• https://github.com/opencontainers/runc/commit/d40b3439a9614a86e87b81a94c6811ec6fa2d7d2
• https://github.com/opencontainers/runc/commit/d61fd29d854b416feaaf128bf650325cd2182165
• https://github.com/opencontainers/runc/commit/db19bbed5348847da433faa9d69e9f90192bfa64
• https://github.com/opencontainers/runc/commit/ed6b1693b8b3ae7eb0250a7e76fc888cdacf98c1
• https://github.com/opencontainers/runc/commit/ff6fe1324663538167eca8b3d3eec61e1bd4fa51
• https://github.com/opencontainers/runc/commit/ff94f9991bd32076c871ef0ad8bc1b763458e480
• https://github.com/opencontainers/runc/security/advisories/GHSA-9493-h29p-rfm2
• https://github.com/opencontainers/runc/security/advisories/GHSA-cgrx-mc8f-2prm
• https://github.com/opencontainers/runc/security/advisories/GHSA-qw9x-cqr3-wc7r