CVE-2025-52881 is a vulnerability in runc that allows an attacker to misdirect writes to procfs files via racing containers with shared mounts, bypassing existing LSM label protections. This can lead to container escape and denial of service by writing to sensitive procfs files such as /proc/sysrq-trigger or sysctl entries like /proc/sys/kernel/core_pattern. The issue affects multiple versions of runc and has been patched in versions 1.2.8, 1.13.0, 1.3.3, and 1.4.0-rc.3. The vulnerability builds on a previous flaw (CVE-2019-19921) but is more sophisticated and allows broader impact. Exploitation could cause host system crashes or privilege escalation by disabling security labels and manipulating kernel behavior.