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.
MITRE ATT&CK mappings
0 exclusive techniques.This is coverage no other published rule has; it is not this rule's total technique count.
References
| Reference | Cited by |
|---|---|
| github.com/Neo23x0/auditd/blob/master/audit.rules | 5from 2 sources |
| github.com/theori-io/copy-fail-CVE-2026-31431 | 3 |
| xint.io/blog/copy-fail-linux-distributions | 4from 2 sources |
From the source
- At source
- Open at source
- Upstream identifier
- dd16294f-44d2-40b4-a869-542c0b85113a
- Tagged by the source as
- Linux Privilege EscalationEndpointendpointSplunk CloudSplunk EnterpriseSplunk Enterprise Securityendpoint
Licence
- Published under
- Apache License 2.0Read the licence
- Attribution
- Required
- Obtained under
- Apache-2.0Read the origin licence
Authorship
- Written by
- Published
- Aug 26, 2026
- Version
- 1