CVE-2025-52881

A flaw was found in runc. This attack is a more sophisticated variant of CVE-2019-16884, which was a flaw that allowed an attacker to trick runc into writing the LSM process labels for a container process into a dummy tmpfs file and thus not apply the correct LSM labels to the container process. The mitigation applied for CVE-2019-16884 was fairly limited and effectively only caused runc to verify that when we write LSM labels that those labels are actual procfs files.

Red Hat considers this as an Important flaw since the impact is limited to local attack with minimal privileges in order to jeopardize the environment.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Potential mitigations for this issue include:

• Using rootless containers, as doing so will block most of the inadvertent writes (runc would run with reduced privileges, making attempts to write to procfs files ineffective).
• Based on our analysis, neither AppArmor or SELinux can protect against the full version of the redirected write attack. The container runtime is generally privileged enough to write to arbitrary procfs files, which is more than sufficient to cause a container breakout.