Bug 2541245 (CVE-2026-97568)

Summary:	CVE-2026-97568 kernel: mptcp: syncookies: remember the request backup flag
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
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 Multipath TCP (MPTCP) implementation. A local attacker could cause a denial of service (DoS) by exploiting an uninitialized memory access during connection handling. When processing connection requests using SYN cookies, the kernel copies uninitialized subflow state information instead of preserving the proper connection flags, leading to kernel instability and potential system crashes.	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 2026-09-25 11:09:54 UTC

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

mptcp: syncookies: remember the request backup flag

Instead of using an uninitialised bit when copying the info in
subflow_ulp_clone().

To fix this, no need to extend the join_entry structure: backup is
coming from struct mptcp_subflow_request_sock, only one bit. Do the same
here by using one bit for both.

Comment 1 gkamathe 2026-09-29 04:06:06 UTC

Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-97568.mbox