Bug 2506691 (CVE-2026-56391)

Summary:	CVE-2026-56391 coreutils: GNU coreutils uniq: Denial of Service and information disclosure via out-of-bounds read with multibyte input
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security <prodsec-ir-bot>
Status:	NEW ---	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	akhatavk, aos-team-art-private, asdas, dpaolell, gtanzill, jbuscemi, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, watson-tool-maintainers
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	---
Doc Text:	A flaw was found in GNU coreutils uniq. When processing specially crafted multibyte input with the --check-chars option, an attacker can trigger an out-of-bounds read. This vulnerability can lead to a denial of service (DoS) due to an application crash and potentially expose sensitive information from adjacent memory.	Story Points:	---
Clone Of:		Environment:
Last Closed:		Type:	---
Regression:	---	Mount Type:	---
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:	2507449
Bug Blocks:

Description OSIDB Bzimport 2026-07-24 09:01:29 UTC

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.

Comment 3 Jon Orris 2026-09-16 09:25:48 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 10

Via RHSA-2026:67886 https://access.redhat.com/errata/RHSA-2026:67886