Linux CVE-2026-31431 "Copy Fail" LPE Enables Stealthy Root Access, Container Escape

CVE-2026-31431 ("Copy Fail") is a high-severity Linux kernel local privilege escalation vulnerability (CVSS 7.8) that permits an unprivileged user to write four controlled bytes into the page cache of readable files, enabling root escalation and container-to-host escapes; it affects kernels back to 4.14 (since 2017) with multiple fixed releases listed and active public proofs-of-concept, and the advisory recommends immediate patching to vendor-supplied fixed kernels, rebooting, or temporarily blacklisting the algif_aead module as mitigation.