CVE-2025-31133 — runc container escape via "masked path" abuse due to mount race conditions

Affected: opencontainers runc

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.

USN-7851-1 — runc-app, runc-stable vulnerabilities

Affected: Ubuntu:22.04:LTS: runc-app, Ubuntu:24.04:LTS: runc-app, Ubuntu:25.10: runc-app, Ubuntu:25.10: runc-stable

Lei Wang and Li Fubang discovered that runC incorrectly handled masked paths. An attacker could possibly replace a container's /dev/null with a symlink to some other procfs file and possibly escape a container. (CVE-2025-31133)

Lei Wang and Li Fubang discovered that runC incorrectly handled the /dev/console bind-mounts. An attacker could potentially exploit this issue to build-mount a symlink and escape a container. (CVE-2025-52565)

Li Fubang and Tõnis Tiigi discovered that the fix for CVE-2019-16884 was incomplete. An attacker could possibly use this issue to cause a denial of service or escape the container. (CVE-2025-52881)

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CVE-2025-31133 — runc container escape via "masked path" abuse due to mount race conditions

USN-7851-1 — runc-app, runc-stable vulnerabilities