GHSA-fqw6-gf59-qr4w

containerd user ID handling bypass allows runAsNonRoot evasion

### Impact A bug was found in containerd where containers launched with a numeric `User` directive that cannot be parsed as a 32-bit integer are incorrectly treated as a username. If a crafted image provides an `/etc/passwd` file mapping this large numeric string to root, the container ultimately runs as root (UID 0). This allows the Kubernetes `runAsNonRoot` restriction to be bypassed, causing unexpected behavior for environments that require containers to run as a non-root user. ### Patches This bug has been fixed in the following containerd versions: * 2.3.1 * 2.2.4 * 2.0.9 * 1.7.32 Note: The containerd 2.1 release has reached its [end of life](https://containerd.io/releases/#current-state-of-containerd-releases) and a fixed version is not provided. Users should update to these versions to resolve the issue. ### Workarounds Ensure that only trusted images are used and that only trusted users have permissions to import images. Alternatively, enforcing a specific numeric `runAsUser` in the Kubernetes Pod `securityContext` overrides the `USER` directive in the image and prevents the bypass. Newer versions of Kubernetes, starting with 1.34, also appear to enforce `runAsNonRoot` properly regardless of this bug. ### Credits The containerd project would like to thank Lei Wang (@ssst0n3) for responsibly disclosing this issue in accordance with the [containerd security policy](https://github.com/containerd/project/blob/main/SECURITY.md). ### Resources * https://github.com/advisories/GHSA-265r-hfxg-fhmg (CVE-2024-40635) ### For more information If there are any questions or comments about this advisory: * Open an issue in [containerd](https://github.com/containerd/containerd/issues/new/choose) * Send an email to [security@containerd.io](mailto:security@containerd.io) To report a security issue in containerd: * [Report a new vulnerability](https://github.com/containerd/containerd/security/advisories/new) * Send an email to [security@containerd.io](mailto:security@containerd.io)