CVE-2026-68376: sctp: fix auth_hmacs array size in struct sctp_cookie

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

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

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

sctp: fix auth_hmacs array size in struct sctp_cookie

The auth_hmacs array in struct sctp_cookie is supposed to store a complete
SCTP_AUTH_HMAC_ALGO parameter, which consists of a struct sctp_paramhdr
followed by N HMAC identifiers.

However, the array size was calculated using an extra 2 bytes instead of
sizeof(struct sctp_paramhdr), which is 4 bytes. When four HMAC identifiers
are configured, the HMAC-ALGO parameter stored in the endpoint is larger
than the auth_hmacs buffer in the cookie.

As a result, sctp_association_init() copies beyond the end of auth_hmacs
when initializing the association, corrupting the adjacent auth_chunks
field. This can lead to an invalid HMAC identifier being accepted and later
cause an out-of-bounds read in sctp_auth_get_hmac().

Fix the array size calculation by including the full SCTP parameter header
size.

The Linux kernel CVE team has assigned CVE-2026-68376 to this issue.


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

	Issue introduced in 2.6.24 with commit 1f485649f52929d9937b346a920a522a7363e202 and fixed in 6.6.148 with commit 0b4414e43e0861d67276031cc21401d7e87de3da
	Issue introduced in 2.6.24 with commit 1f485649f52929d9937b346a920a522a7363e202 and fixed in 6.12.101 with commit d0a59ba58578e2b330fff80a44fe519f3ba7d8c7
	Issue introduced in 2.6.24 with commit 1f485649f52929d9937b346a920a522a7363e202 and fixed in 6.18.42 with commit a8d20ba0ab518c9ccbcde258f25fc1ee6e51d5db
	Issue introduced in 2.6.24 with commit 1f485649f52929d9937b346a920a522a7363e202 and fixed in 7.1.6 with commit 3aa40c3bccac2312ea7cf97f329190637f972b5d
	Issue introduced in 2.6.24 with commit 1f485649f52929d9937b346a920a522a7363e202 and fixed in 7.2-rc4 with commit e0b5252a59383b77d1b8dbeda00b7184dd95f4d3

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-2026-68376
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:
	include/net/sctp/structs.h


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/0b4414e43e0861d67276031cc21401d7e87de3da
	https://git.kernel.org/stable/c/d0a59ba58578e2b330fff80a44fe519f3ba7d8c7
	https://git.kernel.org/stable/c/a8d20ba0ab518c9ccbcde258f25fc1ee6e51d5db
	https://git.kernel.org/stable/c/3aa40c3bccac2312ea7cf97f329190637f972b5d
	https://git.kernel.org/stable/c/e0b5252a59383b77d1b8dbeda00b7184dd95f4d3