CVE-2026-74469: sctp: prevent peer transport count overflow

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

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

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

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

sctp: prevent peer transport count overflow

sctp_assoc_add_peer() increments the association's 16-bit transport_count
for every new unique peer. Adding the 65,536th transport wraps the count to
zero.

SCTP sock_diag uses transport_count to reserve the INET_DIAG_PEERS payload,
then copies one sockaddr_storage for every entry in transport_addr_list.
After the wrap, a diagnostic dump reserves an empty payload and writes
8 MiB of peer addresses past the skb tail.

Reject a new unique peer when transport_count has reached U16_MAX. Perform
the check after the existing-peer lookup so a duplicate address continues
to return its existing transport at the limit.

The Linux kernel CVE team has assigned CVE-2026-74469 to this issue.


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

	Issue introduced in 4.7 with commit 8f840e47f190cbe61a96945c13e9551048d42cef and fixed in 6.6.151 with commit 546221b86ceeba0d8fec92d46a0604bb7b62be07
	Issue introduced in 4.7 with commit 8f840e47f190cbe61a96945c13e9551048d42cef and fixed in 6.12.103 with commit 09e722030e8148ba4ed1e42c6b2ea57bda9f9895
	Issue introduced in 4.7 with commit 8f840e47f190cbe61a96945c13e9551048d42cef and fixed in 6.18.44 with commit 4ba5bf7ed50f235ea4581de8e7a0002f4ed287b0
	Issue introduced in 4.7 with commit 8f840e47f190cbe61a96945c13e9551048d42cef and fixed in 7.1.8 with commit 6201cd1d70f1670c5b31ac506e7ab2fa7b8e7f75
	Issue introduced in 4.7 with commit 8f840e47f190cbe61a96945c13e9551048d42cef and fixed in 7.2-rc6 with commit bd0e9289e2642f6a5c54faad304ce0f41e926d22

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-2026-74469
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/associola.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/546221b86ceeba0d8fec92d46a0604bb7b62be07
	https://git.kernel.org/stable/c/09e722030e8148ba4ed1e42c6b2ea57bda9f9895
	https://git.kernel.org/stable/c/4ba5bf7ed50f235ea4581de8e7a0002f4ed287b0
	https://git.kernel.org/stable/c/6201cd1d70f1670c5b31ac506e7ab2fa7b8e7f75
	https://git.kernel.org/stable/c/bd0e9289e2642f6a5c54faad304ce0f41e926d22