CVE-2026-52981: neigh: let neigh_xmit take skb ownership

CVE-2026-52981: neigh: let neigh_xmit take skb ownership

[Greg Kroah-Hartman]

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

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

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

neigh: let neigh_xmit take skb ownership

neigh_xmit always releases the skb, except when no neighbour table is
found. But even the first added user of neigh_xmit (mpls) relied on
neigh_xmit to release the skb (or queue it for tx).

sashiko reported:
 If neigh_xmit() is called with an uninitialized neighbor table (for
 example, NEIGH_ND_TABLE when IPv6 is disabled), it returns -EAFNOSUPPORT
 and bypasses its internal out_kfree_skb error path.  Because the return
 value of neigh_xmit() is ignored here, does this leak the SKB?

Assume full ownership and remove the last code path that doesn't
xmit or free skb.

The Linux kernel CVE team has assigned CVE-2026-52981 to this issue.


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

	Issue introduced in 4.1 with commit 4fd3d7d9e868ffbdb0e7a67c5c8e9dfdcd846a62 and fixed in 6.1.175 with commit 8a89054a1ec0767aec25ed2bbac933da6ba3cf5a
	Issue introduced in 4.1 with commit 4fd3d7d9e868ffbdb0e7a67c5c8e9dfdcd846a62 and fixed in 6.6.141 with commit 9247d59ca15bf60a57dca08103f055d8a4340877
	Issue introduced in 4.1 with commit 4fd3d7d9e868ffbdb0e7a67c5c8e9dfdcd846a62 and fixed in 6.12.91 with commit 0084712e0bee204b284510cdb63182fd5a30c2b7
	Issue introduced in 4.1 with commit 4fd3d7d9e868ffbdb0e7a67c5c8e9dfdcd846a62 and fixed in 6.18.33 with commit 63063ba60d2dc334e34f1e3f9271d7f3f6f30307
	Issue introduced in 4.1 with commit 4fd3d7d9e868ffbdb0e7a67c5c8e9dfdcd846a62 and fixed in 7.0.10 with commit 445e45a2c3a078316a62d2d331a570cf34ef5079
	Issue introduced in 4.1 with commit 4fd3d7d9e868ffbdb0e7a67c5c8e9dfdcd846a62 and fixed in 7.1 with commit 4438113be604ee67a7bf4f81da6e1cca41332ce4

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-2026-52981
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/core/neighbour.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/8a89054a1ec0767aec25ed2bbac933da6ba3cf5a
	https://git.kernel.org/stable/c/9247d59ca15bf60a57dca08103f055d8a4340877
	https://git.kernel.org/stable/c/0084712e0bee204b284510cdb63182fd5a30c2b7
	https://git.kernel.org/stable/c/63063ba60d2dc334e34f1e3f9271d7f3f6f30307
	https://git.kernel.org/stable/c/445e45a2c3a078316a62d2d331a570cf34ef5079
	https://git.kernel.org/stable/c/4438113be604ee67a7bf4f81da6e1cca41332ce4