Medium [CVE-2026-56391] GNU coreutils uniq: Denial of Service and information disclosure via out-of-bounds read with multibyte input
This medium-severity Red Hat Linux advisory covers CVE-2026-56391 affecting Red Hat Enterprise Linux 10, Red Hat Hardened Images, Red Hat Enterprise Linux 6.
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Summary
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. This vulnerability can lead to a denial of service (DoS) due to an application crash and potentially expose sensitive information from adjacent memory.
Exploitation requires local user interaction to execute `uniq` with the vulnerable options and input. Red Hat severity: Moderate — CVSS 6.1 (CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:H).
Weakness: CWE-125. Affected Red Hat products: Red Hat Enterprise Linux 10; Red Hat Hardened Images; Red Hat Enterprise Linux 6; Red Hat Enterprise Linux 7; Red Hat Enterprise Linux 8; Red Hat Enterprise Linux 9; Red Hat OpenShift Container Platform 4.
Will not fix / out of support: Red Hat Enterprise Linux 6; Red Hat Enterprise Linux 7.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative. Check it before change work.
Official advisory · high-confidence parse· fetched 1 day ago·verify at source
- coreutils-0:9.5-8.el10_2.1
- coreutils-main-9.11-5.1.hum1
- RHSA-2026:67886
- RHSA-2026:46515
Official advisory · high-confidence parse· fetched 1 day ago·verify at source
Mitigation checklist
- Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
Official advisory · high-confidence parse· fetched 1 day ago·verify at source
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