From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-cve-announce@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@kernel.org>
Subject: CVE-2026-97609: netfilter: cttimeout: prevent UAF during module unload
Date: Fri, 25 Sep 2026 12:23:09 +0200 [thread overview]
Message-ID: <2026092501-CVE-2026-97609-db76@gregkh> (raw)
From: Greg Kroah-Hartman <gregkh@kernel.org>
Description
===========
In the Linux kernel, the following vulnerability has been resolved:
netfilter: cttimeout: prevent UAF during module unload
nf_ct_set_timeout() protects the timeout hook dereference and policy lookup
with rcu_read_lock(). cttimeout_exit(), however, unregisters the per-net
operations before it clears the hook.
This allows the following interleaving:
CPU 0 CPU 1
cttimeout_exit() nf_ct_set_timeout()
unregister_pernet_subsys() rcu_read_lock()
kfree(pernet) h = nf_ct_timeout_hook
h->timeout_find_get()
nfct_timeout_pernet()
The hook still points to ctnl_timeout_find_get() when CPU 1 looks up the
already freed per-net timeout list. KASAN reported:
BUG: KASAN: slab-use-after-free in ctnl_timeout_find_get
Read of size 8 by task poc/90
Call Trace:
ctnl_timeout_find_get+0x271/0x2a0 [nfnetlink_cttimeout]
nf_ct_set_timeout+0x7b/0x3c0
xt_ct_tg_check+0x724/0xb20
xt_check_target+0x234/0xa90
do_ipt_set_ctl+0x570/0x1270
Allocated by task 89:
__kmalloc_noprof+0x16e/0x460
ops_init+0x6d/0x420
register_pernet_operations+0x2f6/0x670
Freed by task 91:
kfree+0x131/0x390
ops_undo_list+0x3d4/0x730
unregister_pernet_operations+0x232/0x490
unregister_pernet_subsys+0x1c/0x30
cttimeout_exit+0x52/0x970 [nfnetlink_cttimeout]
Clear the hook and wait for existing readers before unregistering the
per-net operations. This blocks new policy lookups and ensures readers that
observed the hook finish before the per-net storage is freed.
The Linux kernel CVE team has assigned CVE-2026-97609 to this issue.
Affected and fixed versions
===========================
Issue introduced in 5.13 with commit ebfbe67568a734a449203097b02c4ab884257535 and fixed in 6.18.53 with commit a7fdd86c386b7f7cc72a126389c2cdb55d035221
Issue introduced in 5.13 with commit ebfbe67568a734a449203097b02c4ab884257535 and fixed in 7.2.7 with commit 1f69c570a73f2dedf75ea5166d47622d5fa958c1
Issue introduced in 5.13 with commit ebfbe67568a734a449203097b02c4ab884257535 and fixed in 7.3-rc3 with commit fec9b1de0d02de8dafa3cc344bcb91cf28660643
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-2026-97609
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/netfilter/nfnetlink_cttimeout.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/a7fdd86c386b7f7cc72a126389c2cdb55d035221
https://git.kernel.org/stable/c/1f69c570a73f2dedf75ea5166d47622d5fa958c1
https://git.kernel.org/stable/c/fec9b1de0d02de8dafa3cc344bcb91cf28660643
reply other threads:[~2026-09-25 10:26 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=2026092501-CVE-2026-97609-db76@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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.