CVE-2026-68320: sctp: fix auth_chunk_list capacity check in sctp_auth_ep_add_chunkid

From: Greg Kroah-Hartman <[email protected]>

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

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

sctp: fix auth_chunk_list capacity check in sctp_auth_ep_add_chunkid

sctp_auth_ep_add_chunkid() uses SCTP_NUM_CHUNK_TYPES (20) as the
capacity limit for ep->auth_chunk_list, allowing it to hold up to
20 chunk entries (param_hdr.length up to 24). However, the copy
destination asoc->c.auth_chunks in struct sctp_cookie is only
SCTP_AUTH_MAX_CHUNKS (16) entries (20 bytes). When more than 16
chunks are added, sctp_association_init() memcpy overflows the
destination by up to 4 bytes.

Fix by using SCTP_AUTH_MAX_CHUNKS as the capacity limit, matching
the destination capacity.

The Linux kernel CVE team has assigned CVE-2026-68320 to this issue.


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

	Issue introduced in 2.6.24 with commit 1f485649f52929d9937b346a920a522a7363e202 and fixed in 6.6.148 with commit 5a365f1e423444c5da7eb689a8661633dad43e48
	Issue introduced in 2.6.24 with commit 1f485649f52929d9937b346a920a522a7363e202 and fixed in 6.12.101 with commit 886e28e14ab655012779016d251fef53d103aa12
	Issue introduced in 2.6.24 with commit 1f485649f52929d9937b346a920a522a7363e202 and fixed in 6.18.42 with commit 11092d79eb2b7c0068382f72fc2416d1786bb2e0
	Issue introduced in 2.6.24 with commit 1f485649f52929d9937b346a920a522a7363e202 and fixed in 7.1.6 with commit b6ea3dda09eb4d5caf7bbc00f857688cf9e98255
	Issue introduced in 2.6.24 with commit 1f485649f52929d9937b346a920a522a7363e202 and fixed in 7.2-rc5 with commit ff04b26794a16a8a879eb4fd2c02c2d6b03850e9

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-2026-68320
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/auth.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/5a365f1e423444c5da7eb689a8661633dad43e48
	https://git.kernel.org/stable/c/886e28e14ab655012779016d251fef53d103aa12
	https://git.kernel.org/stable/c/11092d79eb2b7c0068382f72fc2416d1786bb2e0
	https://git.kernel.org/stable/c/b6ea3dda09eb4d5caf7bbc00f857688cf9e98255
	https://git.kernel.org/stable/c/ff04b26794a16a8a879eb4fd2c02c2d6b03850e9