Bug 2528761 (CVE-2026-80890)

Summary: CVE-2026-80890 kernel: sctp: reject stale cookies with mismatched verification tags
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: 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   
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Fixed In Version: Doc Type: ---
Doc Text:
A flaw was found in the Stream Control Transmission Protocol (SCTP) implementation within the Linux kernel. The `sctp_unpack_cookie()` function incorrectly skips cookie expiration checks when an association already exists. A remote attacker could exploit this by replaying an expired SCTP cookie with mismatched verification tags, potentially causing an existing association to unexpectedly restart.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
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Description OSIDB Bzimport 2026-09-04 17:26:37 UTC 
In the Linux kernel, the following vulnerability has been resolved:

sctp: reject stale cookies with mismatched verification tags

sctp_unpack_cookie() skips cookie expiration checks whenever an
association already exists.  This is broader than the exception in
RFC 9260 Section 5.2.4.

For an existing association, Section 5.2.4 permits an expired State
Cookie only when both Verification Tags in the cookie match the current
association.  Otherwise, the packet SHOULD be discarded and a Stale
Cookie ERROR MUST be sent.

The broad check lets an expired Action A restart cookie reach
sctp_sf_do_dupcook_a().  In a runtime test with the default 60 second
cookie lifetime, replaying such a cookie after 65 seconds returned a
COOKIE-ACK and restarted the association.

Check cookie expiration unless both Verification Tags match.  This
preserves the Action D exception for a lost COOKIE ACK while rejecting
expired cookies in all other cases.
Comment 1 Mauro Matteo Cascella 2026-09-07 17:17:59 UTC 
Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-80890.mbox