From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-cve-announce@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@kernel.org>
Subject: CVE-2026-43374: net: nexthop: fix percpu use-after-free in remove_nh_grp_entry
Date: Fri, 8 May 2026 16:21:43 +0200 [thread overview]
Message-ID: <2026050830-CVE-2026-43374-385e@gregkh> (raw)
From: Greg Kroah-Hartman <gregkh@kernel.org>
Description
===========
In the Linux kernel, the following vulnerability has been resolved:
net: nexthop: fix percpu use-after-free in remove_nh_grp_entry
When removing a nexthop from a group, remove_nh_grp_entry() publishes
the new group via rcu_assign_pointer() then immediately frees the
removed entry's percpu stats with free_percpu(). However, the
synchronize_net() grace period in the caller remove_nexthop_from_groups()
runs after the free. RCU readers that entered before the publish still
see the old group and can dereference the freed stats via
nh_grp_entry_stats_inc() -> get_cpu_ptr(nhge->stats), causing a
use-after-free on percpu memory.
Fix by deferring the free_percpu() until after synchronize_net() in the
caller. Removed entries are chained via nh_list onto a local deferred
free list. After the grace period completes and all RCU readers have
finished, the percpu stats are safely freed.
The Linux kernel CVE team has assigned CVE-2026-43374 to this issue.
Affected and fixed versions
===========================
Issue introduced in 6.9 with commit f4676ea74b8549cd88dbfe2a592ce4530039e61f and fixed in 6.12.78 with commit abf4feaee6405f1441929c6ebe7a250f2cd170a7
Issue introduced in 6.9 with commit f4676ea74b8549cd88dbfe2a592ce4530039e61f and fixed in 6.18.19 with commit ab5ebab9664214ba41a7633cb4e72f128204f924
Issue introduced in 6.9 with commit f4676ea74b8549cd88dbfe2a592ce4530039e61f and fixed in 6.19.9 with commit 9e08ad731862b22a87cc55f752e16d66cdc9e231
Issue introduced in 6.9 with commit f4676ea74b8549cd88dbfe2a592ce4530039e61f and fixed in 7.0 with commit b2662e7593e94ae09b1cf7ee5f09160a3612bcb2
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-2026-43374
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/ipv4/nexthop.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/abf4feaee6405f1441929c6ebe7a250f2cd170a7
https://git.kernel.org/stable/c/ab5ebab9664214ba41a7633cb4e72f128204f924
https://git.kernel.org/stable/c/9e08ad731862b22a87cc55f752e16d66cdc9e231
https://git.kernel.org/stable/c/b2662e7593e94ae09b1cf7ee5f09160a3612bcb2
reply other threads:[~2026-05-08 14:22 UTC|newest]
Thread overview: [no followups] expand[flat|nested] mbox.gz Atom feed
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=2026050830-CVE-2026-43374-385e@gregkh \
--to=gregkh@linuxfoundation.org \
--cc=cve@kernel.org \
--cc=gregkh@kernel.org \
--cc=linux-cve-announce@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox