CVE-2026-56391

Publication date 24 July 2026

Last updated 31 August 2026

Ubuntu priority

Cvss 3 Severity Score

Description

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.

Read the notes from the security team

Status

Show unmaintained releases

Package	Ubuntu Release	Status
coreutils	26.04 LTS resolute	Vulnerable
	24.04 LTS noble	Not affected
	22.04 LTS jammy	Not affected
	20.04 LTS focal	Not affected
	18.04 LTS bionic	Not affected
	16.04 LTS xenial	Not affected
	14.04 LTS trusty	Not affected

Notes

mdeslaur

issue was introduced in coreutils 9.5

Patch details

For informational purposes only. We recommend not to cherry-pick updates. How can I get the fixes?

Package	Patch details
coreutils	Upstream: ?id=d64

Severity score breakdown

CVSS version:

Base score 4.6 · Medium

Base metrics

Parameter	Value
Attack vector	Local
Attack complexity	Low
Attack requirements	None
Privileges required	None
User interaction	Active
Vulnerable system - Confidentiality impact	Low
Vulnerable system - Integrity impact	None
Vulnerable system - Availability impact	Low
Subsequent system - Confidentiality impact	None
Subsequent system - Integrity impact	None
Subsequent system - Availability impact	None

Scores

Parameter	Value
Base score	4.6 · Medium
Base + Threat score	-
Base + Environmental score	-
Base + Threat + Environmental score	-

Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:L/VI:N/VA:L/SC:N/SI:N/SA:N

Base score 6.1 · Medium