CVE-2026-46054 Linux CVE debrief

Who should care

Organizations running Linux systems with SELinux in enforcing mode and overlayfs mounts, particularly container platforms, build systems, and multi-tenant environments where overlayfs is used for layered filesystem operations. Security teams responsible for mandatory access control policy enforcement and kernel security posture.

Technical summary

The vulnerability exists in SELinux's handling of overlayfs memory operations. Overlayfs presents a unified view of a lower (backing) filesystem and an upper (user) filesystem. SELinux's security model requires dual authorization: the accessing task must have permissions on the user-visible file, and the mounter's credentials must authorize access to the backing file. The implementation gap meant that mmap() and mprotect() operations did not validate backing file permissions, potentially allowing unauthorized memory mappings or protection changes. The fix integrates with the LSM framework through a new hook (security_mmap_backing_file()) and extends the backing file infrastructure to capture and enforce policy decisions during mprotect() calls. This is infrastructure-level hardening rather than a specific exploit vector, but closes a policy enforcement consistency issue that could contribute to privilege escalation chains on SELinux-hardened systems.

Defensive priority

medium

Recommended defensive actions

• Apply kernel updates containing the referenced stable tree commits when available through distribution security channels
• Verify SELinux is enforcing on systems using overlayfs
• Review overlayfs mount configurations for compliance with organizational security policies
• Monitor distribution security advisories for kernel package updates addressing this CVE

Evidence notes

The CVE description confirms this is a resolved vulnerability in the Linux kernel's SELinux subsystem. The fix involves new LSM infrastructure (security_mmap_backing_file() hook, backing file API, new LSM blob) to close the enforcement gap. Two kernel.org stable tree commits are referenced as remediation sources. No CVSS score or severity has been assigned by NVD at time of disclosure.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.