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CVE-2026-72421

CRITICALCVSS 10/10EPSS 0.21%

Last modified

CVE-2026-72421 is a critical-severity vulnerability rated 10/10 on the CVSS scale. 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.. EPSS estimates a 0.21% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1
10/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N

EPSS Probability
0.21%

11.6th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

VendorProductVersions
LinuxLinux>= f4530fa574df4d833506c53697ed1daa0d390bf4, < a29e95fbc51e8a1b932773fd0e259b2080881443; >= f4530fa574df4d833506c53697ed1daa0d390bf4, < 5ae18d87a45698e8244d0fcba64c658c35a7dd3d; >= f4530fa574df4d833506c53697ed1daa0d390bf4, < 9127589aabdee588278e8d0d0bd3709a760a92c8; >= f4530fa574df4d833506c53697ed1daa0d390bf4, < 49eaf1403201357762d745a35882fb734107d763; >= f4530fa574df4d833506c53697ed1daa0d390bf4, < fd25996f57a95d56bc568c89b4921edcf334b7d8; >= f4530fa574df4d833506c53697ed1daa0d390bf4, < 828fad4fd418bcdb9f5d66fec0d184c52a85ec31; >= f4530fa574df4d833506c53697ed1daa0d390bf4, < a668fa160247d7bbe921548cb845f607b8b9305f; >= f4530fa574df4d833506c53697ed1daa0d390bf4, < b72f0db64205d9ce462038ba995d5d31eff32dc1
LinuxLinux3.6

References

Timeline

Published
Last Modified
Status
Received

Frequently Asked Questions

What is 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.
How severe is CVE-2026-72421?
CVE-2026-72421 has a CVSS score of 10/10 (CRITICAL severity). The EPSS model estimates a 0.21% probability of exploitation in the next 30 days.
How do I fix CVE-2026-72421?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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Source: NVD / NIST