linux-cve-announce - CVE-2025-68363: bpf: Check skb->transport_header is set in bpf_skb_check

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [day] [month] [year] [list]

Message-ID: <2025122458-CVE-2025-68363-3863@gregkh>
Date: Wed, 24 Dec 2025 11:35:08 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-68363: bpf: Check skb->transport_header is set in bpf_skb_check_mtu

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

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

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

bpf: Check skb->transport_header is set in bpf_skb_check_mtu

The bpf_skb_check_mtu helper needs to use skb->transport_header when
the BPF_MTU_CHK_SEGS flag is used:

	bpf_skb_check_mtu(skb, ifindex, &mtu_len, 0, BPF_MTU_CHK_SEGS)

The transport_header is not always set. There is a WARN_ON_ONCE
report when CONFIG_DEBUG_NET is enabled + skb->gso_size is set +
bpf_prog_test_run is used:

WARNING: CPU: 1 PID: 2216 at ./include/linux/skbuff.h:3071
 skb_gso_validate_network_len
 bpf_skb_check_mtu
 bpf_prog_3920e25740a41171_tc_chk_segs_flag # A test in the next patch
 bpf_test_run
 bpf_prog_test_run_skb

For a normal ingress skb (not test_run), skb_reset_transport_header
is performed but there is plan to avoid setting it as described in
commit 2170a1f09148 ("net: no longer reset transport_header in __netif_receive_skb_core()").

This patch fixes the bpf helper by checking
skb_transport_header_was_set(). The check is done just before
skb->transport_header is used, to avoid breaking the existing bpf prog.
The WARN_ON_ONCE is limited to bpf_prog_test_run, so targeting bpf-next.

The Linux kernel CVE team has assigned CVE-2025-68363 to this issue.


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

	Issue introduced in 5.12 with commit 34b2021cc61642d61c3cf943d9e71925b827941b and fixed in 6.12.63 with commit 30ce906557a21adef4cba5901c8e995dc18263a9
	Issue introduced in 5.12 with commit 34b2021cc61642d61c3cf943d9e71925b827941b and fixed in 6.17.13 with commit 1c30e4afc5507f0069cc09bd561e510e4d97fbf7
	Issue introduced in 5.12 with commit 34b2021cc61642d61c3cf943d9e71925b827941b and fixed in 6.18.2 with commit 942268e2726ac7f16e3ec49dbfbbbe7cf5af9da5
	Issue introduced in 5.12 with commit 34b2021cc61642d61c3cf943d9e71925b827941b and fixed in 6.19-rc1 with commit d946f3c98328171fa50ddb908593cf833587f725

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-2025-68363
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/filter.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/30ce906557a21adef4cba5901c8e995dc18263a9
	https://git.kernel.org/stable/c/1c30e4afc5507f0069cc09bd561e510e4d97fbf7
	https://git.kernel.org/stable/c/942268e2726ac7f16e3ec49dbfbbbe7cf5af9da5
	https://git.kernel.org/stable/c/d946f3c98328171fa50ddb908593cf833587f725