CVE-2026-64414: netfilter: handle unreadable frags

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

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

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

netfilter: handle unreadable frags

sashiko reports:
 When an skb with unreadable fragments (such as from devmem TCP, where
 skb_frags_readable(skb) returns false) is processed by the u32 module,
 skb_copy_bits() will safely return a negative error code [..]

xt_u32: bail out with hotdrop in this case.
gather_frags: return -1, just as if we had no fragment header.
nfnetlink_queue: restrict to the linear part.
nfnetlink_log: restrict to the linear part.

v2:
 - skb_zerocopy helpers don't copy readable flag, i.e. nfnetlink_queue
 is broken too
 xt_u32 shouldn't return true if hotdrop was set.

The Linux kernel CVE team has assigned CVE-2026-64414 to this issue.


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

	Issue introduced in 6.12 with commit 65249feb6b3df9e17bab5911ee56fa7b0971e231 and fixed in 6.12.96 with commit 3b13e7635795394705920cca1e1db7e4ca2e334b
	Issue introduced in 6.12 with commit 65249feb6b3df9e17bab5911ee56fa7b0971e231 and fixed in 6.18.39 with commit fc5bfe63bacf8a3ae307b62b34206406ca733354
	Issue introduced in 6.12 with commit 65249feb6b3df9e17bab5911ee56fa7b0971e231 and fixed in 7.1.4 with commit 57056be3ec12e7d9ecd20a60d4060f510e4f284c
	Issue introduced in 6.12 with commit 65249feb6b3df9e17bab5911ee56fa7b0971e231 and fixed in 7.2-rc3 with commit da5b58478a9c1b85608c9e40a3b8432d071b409e

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-2026-64414
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/ipv6/netfilter/nf_conntrack_reasm.c
	net/netfilter/nfnetlink_log.c
	net/netfilter/nfnetlink_queue.c
	net/netfilter/xt_u32.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/3b13e7635795394705920cca1e1db7e4ca2e334b
	https://git.kernel.org/stable/c/fc5bfe63bacf8a3ae307b62b34206406ca733354
	https://git.kernel.org/stable/c/57056be3ec12e7d9ecd20a60d4060f510e4f284c
	https://git.kernel.org/stable/c/da5b58478a9c1b85608c9e40a3b8432d071b409e