Stack Buffer Overflow DoS in GNU cpio (tar/ustar)
CVE-2026-126831 Published on November 12, 2026
Cpio: cpio: stack-based buffer overflow in write_out_tar_header() with long usernames/groupnames
A flaw was found in cpio. A local user can cause a Denial of Service (DoS) by triggering a stack-based buffer overflow when creating archives in tar or ustar formats. When archiving files owned by users or groups with names exceeding 32 characters, cpio copies these names into fixed-size memory without verifying their length. This unbounded copy corrupts stack memory and causes the application to crash.
Vulnerability Analysis
CVE-2026-126831 can be exploited with local system access, and requires small amount of user privileges. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality and integrity, and a high impact on availability.
Timeline
Reported to Red Hat.
Made public.
Weakness Type
What is a Stack Overflow Vulnerability?
A stack-based buffer overflow condition is a condition where the buffer being overwritten is allocated on the stack (i.e., is a local variable or, rarely, a parameter to a function).
CVE-2026-126831 has been classified to as a Stack Overflow vulnerability or weakness.
Products Associated with CVE-2026-126831
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Affected Versions
Red Hat Enterprise Linux 10: Red Hat Enterprise Linux 6: Red Hat Enterprise Linux 7: Red Hat Enterprise Linux 8: Red Hat Enterprise Linux 9: Red Hat Hardened Images:Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.