linux-cve-announce - CVE-2026-23171: bonding: fix use-after-free due to enslave fail after slave array update

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Message-ID: <2026021421-CVE-2026-23171-5a73@gregkh>
Date: Sat, 14 Feb 2026 17:04:37 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2026-23171: bonding: fix use-after-free due to enslave fail after slave array update

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

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

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

bonding: fix use-after-free due to enslave fail after slave array update

Fix a use-after-free which happens due to enslave failure after the new
slave has been added to the array. Since the new slave can be used for Tx
immediately, we can use it after it has been freed by the enslave error
cleanup path which frees the allocated slave memory. Slave update array is
supposed to be called last when further enslave failures are not expected.
Move it after xdp setup to avoid any problems.

It is very easy to reproduce the problem with a simple xdp_pass prog:
 ip l add bond1 type bond mode balance-xor
 ip l set bond1 up
 ip l set dev bond1 xdp object xdp_pass.o sec xdp_pass
 ip l add dumdum type dummy

Then run in parallel:
 while :; do ip l set dumdum master bond1 1>/dev/null 2>&1; done;
 mausezahn bond1 -a own -b rand -A rand -B 1.1.1.1 -c 0 -t tcp "dp=1-1023, flags=syn"

The crash happens almost immediately:
 [  605.602850] Oops: general protection fault, probably for non-canonical address 0xe0e6fc2460000137: 0000 [#1] SMP KASAN NOPTI
 [  605.602916] KASAN: maybe wild-memory-access in range [0x07380123000009b8-0x07380123000009bf]
 [  605.602946] CPU: 0 UID: 0 PID: 2445 Comm: mausezahn Kdump: loaded Tainted: G    B               6.19.0-rc6+ #21 PREEMPT(voluntary)
 [  605.602979] Tainted: [B]=BAD_PAGE
 [  605.602998] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
 [  605.603032] RIP: 0010:netdev_core_pick_tx+0xcd/0x210
 [  605.603063] Code: 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 3e 01 00 00 48 b8 00 00 00 00 00 fc ff df 4c 8b 6b 08 49 8d 7d 30 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 25 01 00 00 49 8b 45 30 4c 89 e2 48 89 ee 48 89
 [  605.603111] RSP: 0018:ffff88817b9af348 EFLAGS: 00010213
 [  605.603145] RAX: dffffc0000000000 RBX: ffff88817d28b420 RCX: 0000000000000000
 [  605.603172] RDX: 00e7002460000137 RSI: 0000000000000008 RDI: 07380123000009be
 [  605.603199] RBP: ffff88817b541a00 R08: 0000000000000001 R09: fffffbfff3ed8c0c
 [  605.603226] R10: ffffffff9f6c6067 R11: 0000000000000001 R12: 0000000000000000
 [  605.603253] R13: 073801230000098e R14: ffff88817d28b448 R15: ffff88817b541a84
 [  605.603286] FS:  00007f6570ef67c0(0000) GS:ffff888221dfa000(0000) knlGS:0000000000000000
 [  605.603319] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 [  605.603343] CR2: 00007f65712fae40 CR3: 000000011371b000 CR4: 0000000000350ef0
 [  605.603373] Call Trace:
 [  605.603392]  <TASK>
 [  605.603410]  __dev_queue_xmit+0x448/0x32a0
 [  605.603434]  ? __pfx_vprintk_emit+0x10/0x10
 [  605.603461]  ? __pfx_vprintk_emit+0x10/0x10
 [  605.603484]  ? __pfx___dev_queue_xmit+0x10/0x10
 [  605.603507]  ? bond_start_xmit+0xbfb/0xc20 [bonding]
 [  605.603546]  ? _printk+0xcb/0x100
 [  605.603566]  ? __pfx__printk+0x10/0x10
 [  605.603589]  ? bond_start_xmit+0xbfb/0xc20 [bonding]
 [  605.603627]  ? add_taint+0x5e/0x70
 [  605.603648]  ? add_taint+0x2a/0x70
 [  605.603670]  ? end_report.cold+0x51/0x75
 [  605.603693]  ? bond_start_xmit+0xbfb/0xc20 [bonding]
 [  605.603731]  bond_start_xmit+0x623/0xc20 [bonding]

The Linux kernel CVE team has assigned CVE-2026-23171 to this issue.


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

	Issue introduced in 5.15 with commit 9e2ee5c7e7c35d195e2aa0692a7241d47a433d1e and fixed in 6.18.9 with commit bd25b092a06a3e05f7e8bd6da6fa7318777d8c3d
	Issue introduced in 5.15 with commit 9e2ee5c7e7c35d195e2aa0692a7241d47a433d1e and fixed in 6.19 with commit e9acda52fd2ee0cdca332f996da7a95c5fd25294

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-2026-23171
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:
	drivers/net/bonding/bond_main.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/bd25b092a06a3e05f7e8bd6da6fa7318777d8c3d
	https://git.kernel.org/stable/c/e9acda52fd2ee0cdca332f996da7a95c5fd25294