Critical Linux Vulnerability 'Copy Fail' Grants Root Access Across Major Distros

• •CVE-2026-31431 allows local users to gain root access on Linux systems since 2017.
• •The exploit is a 732-byte Python script that modifies the page cache without altering the disk file.
• •Patches are available, and immediate updates are recommended for affected distributions.

A newly disclosed vulnerability in the Linux kernel, tracked as CVE-2026-31431 and named 'Copy Fail', allows unprivileged local users to gain root access on virtually all major Linux distributions released since 2017. The exploit, which is a 732-byte Python script, modifies the page cache of any readable file without altering the on-disk version, making it stealthy and difficult to detect. Discovered by Theori researcher Taeyang Lee using AI-assisted tools, the flaw stems from a logic error in the kernel's cryptographic subsystem, specifically within the algif_aead module. Patches were made available on April 1, 2026, following the initial disclosure on March 23, 2026, with public proof-of-concept released on April 30, 2026. The vulnerability poses a significant risk, especially in multi-tenant environments like cloud services and Kubernetes, where it can enable container escapes. Security teams are urged to apply patches immediately to mitigate risks associated with this critical flaw.