CVE-2026-72421
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.
Affected versions
Linux kernel versions
3.6
and later are affected. Fixed in
5.10.261,
5.15.212,
6.1.178,
6.6.145,
6.12.97,
6.18.40,
7.1.5,
7.2-rc1
and their respective stable series.
References
8 totalFrequently asked questions
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What is CVE-2026-72421?
CVE-2026-72421 is a unscored severity Linux kernel vulnerability . It affects Linux kernel versions from 3.6 onward and has been patched in 5.10.261, 5.15.212, 6.1.178 and others. CVE-2026-72421 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.
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Is there a patch available for CVE-2026-72421?
Yes. CVE-2026-72421 has been patched. Fixed versions include 5.10.261, 5.15.212, 6.1.178 and others. If you are running Linux kernel 3.6 or later up to the fix versions, apply the relevant patch for your kernel branch.
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Is CVE-2026-72421 actively exploited?
No. CVE-2026-72421 has not been confirmed as actively exploited. It is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.