CVE-2026-80586: mptcp: options: reset DSS fields in case of unexpected size

CVE-2026-80586: mptcp: options: reset DSS fields in case of unexpected size

[Greg Kroah-Hartman]

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

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

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

mptcp: options: reset DSS fields in case of unexpected size

A remote peer could send a malformed DSS with a wrong size, followed by
another DSS or MPC + Data. In this case, the first suboption will be
ignored, but leaving some fields written, which could lead to
inconsistency or access uninitialized data.

Explicitly reset the fields that could have been modified in case of
unexpected size.

The Linux kernel CVE team has assigned CVE-2026-80586 to this issue.


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

	Issue introduced in 5.6 with commit 648ef4b88673dadb8463bf0d4b10fbf33d55def8 and fixed in 5.10.266 with commit 15e35fdad7a5576bf3f1c8d688877aeb5d1b506b
	Issue introduced in 5.6 with commit 648ef4b88673dadb8463bf0d4b10fbf33d55def8 and fixed in 5.15.217 with commit b1256090816ec46011601e084be580731df58fc7
	Issue introduced in 5.6 with commit 648ef4b88673dadb8463bf0d4b10fbf33d55def8 and fixed in 6.1.184 with commit 192878df582c51d440bf7b91a15f297f29f2b596
	Issue introduced in 5.6 with commit 648ef4b88673dadb8463bf0d4b10fbf33d55def8 and fixed in 6.6.153 with commit 26dac5c9ffb20812b475fdf253eb04fab99cff3b
	Issue introduced in 5.6 with commit 648ef4b88673dadb8463bf0d4b10fbf33d55def8 and fixed in 6.12.105 with commit 4e80eff5c1c893aca2ac1d202f0b256d2e52ecde
	Issue introduced in 5.6 with commit 648ef4b88673dadb8463bf0d4b10fbf33d55def8 and fixed in 6.18.46 with commit 1fade1b2ac5b1a4948e538fae7313bea57b5ac36
	Issue introduced in 5.6 with commit 648ef4b88673dadb8463bf0d4b10fbf33d55def8 and fixed in 7.1.10 with commit 27ed642a4e7e4b5df4b8522c72c457a67e052493
	Issue introduced in 5.6 with commit 648ef4b88673dadb8463bf0d4b10fbf33d55def8 and fixed in 7.2 with commit 35772b4981f38ba8059372cde8753e8e477e98ec

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-2026-80586
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/mptcp/options.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/15e35fdad7a5576bf3f1c8d688877aeb5d1b506b
	https://git.kernel.org/stable/c/b1256090816ec46011601e084be580731df58fc7
	https://git.kernel.org/stable/c/192878df582c51d440bf7b91a15f297f29f2b596
	https://git.kernel.org/stable/c/26dac5c9ffb20812b475fdf253eb04fab99cff3b
	https://git.kernel.org/stable/c/4e80eff5c1c893aca2ac1d202f0b256d2e52ecde
	https://git.kernel.org/stable/c/1fade1b2ac5b1a4948e538fae7313bea57b5ac36
	https://git.kernel.org/stable/c/27ed642a4e7e4b5df4b8522c72c457a67e052493
	https://git.kernel.org/stable/c/35772b4981f38ba8059372cde8753e8e477e98ec