Bug 2532035 (CVE-2026-89476)

Summary:	CVE-2026-89476 kernel: sctp: fix stream->outcnt underflow on duplicate RECONF responses
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, 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:
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Doc Text:	A flaw was found in the Linux kernel's Stream Control Transmission Protocol (SCTP) implementation. A remote attacker could exploit this by sending specially crafted duplicate RECONF responses. This action can cause an underflow in the `stream->outcnt` counter, potentially leading to unexpected system behavior or a denial of service (DoS) condition.	Story Points:	---
Clone Of:		Environment:
Last Closed:		Type:	---
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Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2026-09-11 20:08:16 UTC

In the Linux kernel, the following vulnerability has been resolved:

sctp: fix stream->outcnt underflow on duplicate RECONF responses

A cached RECONF chunk may contain more than one request parameter.  A
duplicate response can therefore find and process the same ADD_OUT request
again while another parameter is still outstanding, rolling back outcnt
twice and possibly underflowing it.

Track outstanding request types as bits and clear each bit after its first
response.  Later responses for the same request are then ignored.

Comment 1 Mauro Matteo Cascella 2026-09-14 14:12:00 UTC

Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-89476.mbox