CVE-2026-46680: 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 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.
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 Send an email to security@containerd.io
To report a security issue in containerd: Report a new vulnerability Send an email to security@containerd.io
Other sources
containerd is an open-source container runtime. In versions prior to 1.7.32, 2.0.9, 2.2.4 and 2.3.1, containers launched with a numeric User directive that cannot be parsed as a 32-bit integer are incorrectly treated as a username, leading to runAsNonRoot evasion. 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. This issue has been fixed in versions 1.7.32, 2.0.9, 2.2.4 and 2.3.1.
— MITRE
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
go/github.com/containerd/containerd/v2to a version that resolves this vulnerability.Fixed in 2.3.1 - Upgrade
Upgrade
go/github.com/containerd/containerd/v2to a version that resolves this vulnerability.Fixed in 2.2.4 - Upgrade
Upgrade
go/github.com/containerd/containerd/v2to a version that resolves this vulnerability.Fixed in 2.0.9 - Upgrade
Upgrade
go/github.com/containerd/containerdto a version that resolves this vulnerability.Fixed in 1.7.32 - Upgrade
Upgrade
containerdto a version that resolves this vulnerability.Fixed in 1.7.32 - Upgrade
Upgrade
containerdto a version that resolves this vulnerability.Fixed in 2.0.9 - Upgrade
Upgrade
containerdto a version that resolves this vulnerability.Fixed in 2.2.4 - Upgrade
Upgrade
containerdto a version that resolves this vulnerability.Fixed in 2.3.1 - Configuration
Enforce a specific numeric runAsUser in the Pod securityContext to override the image USER directive and prevent the runAsNonRoot bypass.
Kubernetes Pod securityContext runAsUser = (set an explicit numeric runAsUser) - Compensating control
Ensure only trusted images are used and that only trusted users have permissions to import images, to reduce the risk of crafted images mapping a large numeric USER value to root via /etc/passwd.
Event History
Frequently Asked Questions
What is the severity of CVE-2026-46680?
CVE-2026-46680 has a risk score of 48, indicating a significant vulnerability that should be addressed.
How do I fix CVE-2026-46680?
To fix CVE-2026-46680, ensure the numeric 'User' directive in containerd is properly validated to avoid parsing issues.
What type of systems are affected by CVE-2026-46680?
CVE-2026-46680 affects systems using containerd with improperly configured numeric 'User' directives.
What is the potential impact of CVE-2026-46680?
The potential impact of CVE-2026-46680 includes unauthorized privilege escalation when a crafted container image maps a numeric string to root.
How can I mitigate risks from CVE-2026-46680?
Mitigation for CVE-2026-46680 includes reviewing and restricting the use of improper numeric values in user directives within containerd.