CVE-2025-31133

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 containers /dev/null) was actually a real /dev/null inode when using the containers /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.

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

• https://github.com/opencontainers/runc/commit/1a30a8f3d921acbbb6a4bb7e99da2c05f8d48522
• https://github.com/opencontainers/runc/commit/5d7b2424072449872d1cd0c937f2ca25f418eb66
• https://github.com/opencontainers/runc/commit/8476df83b534a2522b878c0507b3491def48db9f
• https://github.com/opencontainers/runc/commit/db19bbed5348847da433faa9d69e9f90192bfa64
• https://github.com/opencontainers/runc/security/advisories/GHSA-9493-h29p-rfm2