Copy Fail (CVE-2026-31431): Frequently asked questions about Linux kernel privilege escalation vulnerability

**Executive summary:** Tenable Research details CVE-2026-31431 (“Copy Fail”), a high-severity (CVSSv3 7.8) Linux kernel local privilege escalation introduced in 2017 and affecting kernels 4.14 and later; a reliable public proof-of-concept exploit is available, the flaw can modify the kernel page cache to escalate to root and cross container boundaries, and patches or mitigations exist though some distributions had not yet shipped updates as of the report.