Quick answers
- Is CVE-2026-126831 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-126831 being exploited in the wild.
- How severe is CVE-2026-126831?
- Medium severity, with a CVSS score of 5.5, published 12 November 2026.
- Which products and versions are affected?
- GNU cpio.
- Is there a fix for CVE-2026-126831?
- No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
- How is CVE-2026-126831 attacked?
- It is attacked with local access, in a software library.
- Am I affected by CVE-2026-126831?
- Check whether you run Gnu Cpio. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
Technical details
A stack-based buffer overflow exists in cpio's write_out_tar_header() function when processing tar or ustar archive formats. The vulnerability occurs because cpio copies user and group names into fixed 32-character buffers without length validation, allowing an attacker with local access to corrupt stack memory and crash the application. This is a CWE-121 stack-based buffer overflow with local attack vector and low privilege requirements.
Affected products
- GNU cpio
Timeline
- 2026-11-12: disclosed