From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-cve-announce@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@kernel.org>
Subject: CVE-2026-72421: ipv4: fib: Don't ignore error route in local/main tables.
Date: Sat, 15 Aug 2026 15:08:20 +0900 [thread overview]
Message-ID: <2026081525-CVE-2026-72421-d299@gregkh> (raw)
From: Greg Kroah-Hartman <gregkh@kernel.org>
Description
===========
In the Linux kernel, the following vulnerability has been resolved:
ipv4: fib: Don't ignore error route in local/main tables.
When CONFIG_IP_MULTIPLE_TABLES is enabled but no rule is added,
fib_lookup() performs route lookup directly on two tables.
Since the first lookup does not properly bail out, the result
of an error route in the merged local/main table could be
overwritten by another route in the default table:
# unshare -n
# ip link set lo up
# ip route add 192.168.0.0/24 dev lo table 253
# ip route add unreachable 192.168.0.0/24
# ip route get 192.168.0.1
192.168.0.1 dev lo table default uid 0
cache <local>
Once a random rule is added, the error route is respected:
# ip rule add table 0
# ip rule del table 0
# ip route get 192.168.0.1
RTNETLINK answers: No route to host
Let's fix the inconsistent behaviour.
The Linux kernel CVE team has assigned CVE-2026-72421 to this issue.
Affected and fixed versions
===========================
Issue introduced in 3.6 with commit f4530fa574df4d833506c53697ed1daa0d390bf4 and fixed in 5.10.261 with commit a29e95fbc51e8a1b932773fd0e259b2080881443
Issue introduced in 3.6 with commit f4530fa574df4d833506c53697ed1daa0d390bf4 and fixed in 5.15.212 with commit 5ae18d87a45698e8244d0fcba64c658c35a7dd3d
Issue introduced in 3.6 with commit f4530fa574df4d833506c53697ed1daa0d390bf4 and fixed in 6.1.178 with commit 9127589aabdee588278e8d0d0bd3709a760a92c8
Issue introduced in 3.6 with commit f4530fa574df4d833506c53697ed1daa0d390bf4 and fixed in 6.6.145 with commit 49eaf1403201357762d745a35882fb734107d763
Issue introduced in 3.6 with commit f4530fa574df4d833506c53697ed1daa0d390bf4 and fixed in 6.12.97 with commit fd25996f57a95d56bc568c89b4921edcf334b7d8
Issue introduced in 3.6 with commit f4530fa574df4d833506c53697ed1daa0d390bf4 and fixed in 6.18.40 with commit 828fad4fd418bcdb9f5d66fec0d184c52a85ec31
Issue introduced in 3.6 with commit f4530fa574df4d833506c53697ed1daa0d390bf4 and fixed in 7.1.5 with commit a668fa160247d7bbe921548cb845f607b8b9305f
Issue introduced in 3.6 with commit f4530fa574df4d833506c53697ed1daa0d390bf4 and fixed in 7.2-rc1 with commit b72f0db64205d9ce462038ba995d5d31eff32dc1
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-2026-72421
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:
include/net/ip_fib.h
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/a29e95fbc51e8a1b932773fd0e259b2080881443
https://git.kernel.org/stable/c/5ae18d87a45698e8244d0fcba64c658c35a7dd3d
https://git.kernel.org/stable/c/9127589aabdee588278e8d0d0bd3709a760a92c8
https://git.kernel.org/stable/c/49eaf1403201357762d745a35882fb734107d763
https://git.kernel.org/stable/c/fd25996f57a95d56bc568c89b4921edcf334b7d8
https://git.kernel.org/stable/c/828fad4fd418bcdb9f5d66fec0d184c52a85ec31
https://git.kernel.org/stable/c/a668fa160247d7bbe921548cb845f607b8b9305f
https://git.kernel.org/stable/c/b72f0db64205d9ce462038ba995d5d31eff32dc1
reply other threads:[~2026-08-15 6:29 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=2026081525-CVE-2026-72421-d299@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.