2026-005: High Vulnerability in the Linux Kernel ("Copy Fail")

On 29 April 2026, a high local privilege escalation vulnerability in the Linux kernel, tracked as CVE-2026-31431 and named "Copy Fail", was publicly disclosed. The vulnerability affects every mainstream Linux distributions shipping a kernel built since 2017. A public proof-of-concept exploit has been released. As of the date of this advisory, no distribution has shipped a fixed kernel package. The mainline fix was committed on 1 April 2026, but vendor updates are still pending across all major distributions. CERT-EU strongly recommends applying the interim mitigation immediately, prioritising Kubernetes nodes, and CI/CD runners exposed to untrusted workloads.