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Linux Auditd Copy Fail Privilege Escalation

Detects the exploitation pattern associated with Copy Fail. Copy Fail (CVE-2026-31431) is a logic bug in the Linux kernel's authentication cryptographic template. It lets an unprivileged local user trigger a…

Description

Detects the exploitation pattern associated with Copy Fail. Copy Fail (CVE-2026-31431) is a logic bug in the Linux kernel's authentication cryptographic template. It lets an unprivileged local user trigger a deterministic, controlled 4-byte write into the page cache of any readable file on the system. A single 732-byte Python script can edit a setuid binary and obtain root on essentially all Linux distributions shipped since 2017. This search relies on the auditd configuration linked in the references section. If you are using a custom configuration, make sure the Key names are the same or adapt the search accordingly.

Detection logic

Detection requirements

Platform
ContainersLinuxmacOSWindows

The rule states no platform. This is derived from the ATT&CK technique it maps to.

Log source category
linux_auditd_syscall

Known benign triggers

  • No false positives have been identified at this time.

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