CVE-2026-80890: sctp: reject stale cookies with mismatched verification tags

CVE-2026-80890: sctp: reject stale cookies with mismatched verification tags

[Greg Kroah-Hartman]

From: Greg Kroah-Hartman <gregkh@kernel.org>

Description
===========

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.

The Linux kernel CVE team has assigned CVE-2026-80890 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 2.6.12 with commit 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and fixed in 5.10.265 with commit f6e3cc296372accad4ee57405195021231ef4bcb
	Issue introduced in 2.6.12 with commit 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and fixed in 5.15.216 with commit c151daba0ceb1fb068a215b07de89fb1eb5f87bc
	Issue introduced in 2.6.12 with commit 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and fixed in 6.1.183 with commit 817cffdbdbdf50e1f2b016599d1897de3ca54964
	Issue introduced in 2.6.12 with commit 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and fixed in 6.6.151 with commit 61baa5020b0afb41bfd97f8f6ce5e336c4a4546e
	Issue introduced in 2.6.12 with commit 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and fixed in 6.12.103 with commit c68557a49e960dbcdede22c7a9b488603078b8b4
	Issue introduced in 2.6.12 with commit 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and fixed in 6.18.44 with commit a0d1693923f41d6f49083aa2446686aed09d1d79
	Issue introduced in 2.6.12 with commit 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and fixed in 7.1.8 with commit 35c279113498d19a8734e2aae67b951b9b20f634
	Issue introduced in 2.6.12 with commit 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and fixed in 7.2 with commit 9d8da8e0a9bce4a340af60dd0446bc7eb8d07587

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2026-80890
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	net/sctp/sm_make_chunk.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/f6e3cc296372accad4ee57405195021231ef4bcb
	https://git.kernel.org/stable/c/c151daba0ceb1fb068a215b07de89fb1eb5f87bc
	https://git.kernel.org/stable/c/817cffdbdbdf50e1f2b016599d1897de3ca54964
	https://git.kernel.org/stable/c/61baa5020b0afb41bfd97f8f6ce5e336c4a4546e
	https://git.kernel.org/stable/c/c68557a49e960dbcdede22c7a9b488603078b8b4
	https://git.kernel.org/stable/c/a0d1693923f41d6f49083aa2446686aed09d1d79
	https://git.kernel.org/stable/c/35c279113498d19a8734e2aae67b951b9b20f634
	https://git.kernel.org/stable/c/9d8da8e0a9bce4a340af60dd0446bc7eb8d07587