CVE-2026-80588: mptcp: reclaim forward-allocated memory on RX path errors

CVE-2026-80588: mptcp: reclaim forward-allocated memory on RX path errors

[Greg Kroah-Hartman]

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

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

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

mptcp: reclaim forward-allocated memory on RX path errors

After commit 9db5b3cec4ec ("mptcp: borrow forward memory from subflow"),
errors in the receive path prior to queueing skbs into the receive
queue do not trigger forward-allocated memory reclaiming.

Prevent forward memory from growing unboundedly in pathological drop
scenarios by explicitly reclaiming memory when skbs are dropped.

The Linux kernel CVE team has assigned CVE-2026-80588 to this issue.


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

	Issue introduced in 6.18.35 with commit a84164847b1e0a106ebc46821e5d2f9b775c9dc8 and fixed in 6.18.46 with commit 473f1a5ab2abc98dd9e74b95b9c23c66c47535cc
	Issue introduced in 6.19 with commit 9db5b3cec4ec1c0cd3239689f5c8653d691a1754 and fixed in 7.1.10 with commit 8277f48a06d3aa1441f6d0b6998ccc0360d30ed8
	Issue introduced in 6.19 with commit 9db5b3cec4ec1c0cd3239689f5c8653d691a1754 and fixed in 7.2 with commit 41b49a8b914ec7dcb03eae93fb27f3c464078644

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-2026-80588
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/protocol.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/473f1a5ab2abc98dd9e74b95b9c23c66c47535cc
	https://git.kernel.org/stable/c/8277f48a06d3aa1441f6d0b6998ccc0360d30ed8
	https://git.kernel.org/stable/c/41b49a8b914ec7dcb03eae93fb27f3c464078644