Out-of-bounds Read in GNU Coreutils
CVE-2026-56391
GNU coreutils uniq is vulnerable to an out‑of‑bounds read due to incorrect handling of multibyte input when the -w (--check-chars) option is used. The find_field() function miscalculates the byte length of characters by repeatedly processing a fixed pointer instead of advancing through the input, resulting in an inflated length value. This incorrect length is later used in a memcmp operation, causing reads beyond the allocated buffer when processing crafted multibyte input. When running GNU coreutils uniq with attacker-provided arguments, this behavior leads to a crash and potential adjacent heap memory exposure. This issue has been fixed in the commit d64e35a8a4c0e4608321433e0d84d917e4e36371.
Vulnerability class: Buffer Overflow
Published · last modified .
CVSS v3 metric
CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:H.
EPSS exploit prediction
EPSS: 0.002 (6.1th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 6th percentile — 6.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.002 · change: 0.000
Affected products
- GNU Coreutils — versions 9.5
Weakness classification (CWE)
References
- cert.pl/en/posts/2026/07/CVE-2026-56391 (Third Party Advisory, third-party-advisory)
- git.savannah.gnu.org/cgit/coreutils.git/ (Product, product)
- git.savannah.gnu.org/cgit/coreutils.git/commit/ (Patch, patch)
Frequently asked questions
- What is CVE-2026-56391?
- CVE-2026-56391 is a medium-severity vulnerability in GNU Coreutils, classified under Out-of-bounds Read. CVSS score: 6.1/10. Published 2026-07-24.
- How severe is CVE-2026-56391?
- Medium severity. CVSS v3 base score is 6.1 out of 10.