CVE-2025-52881: runc: LSM labels can be bypassed with malicious config using dummy procfs files

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.8% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2025-11-06 · updated 2026-10-07
Weakness: CWE-61

Description

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.

Affected products

opencontainers runc: before 1.2.8; from 1.3.0 before 1.3.3; 1.4.0-rc1, 1.4.0-rc2 — fixed in 1.2.8, 1.3.3

How to fix

Upgrade to a fixed version: opencontainers runc 1.2.8, 1.3.3. Check the vendor advisory for mitigations.

References

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