CVE-2026-72421
CriticalCVSS 10.0Exploitation Probability (EPSS)
Low risk12th percentile - higher than 12% of all known CVEs
Summary
In the Linux kernel IPv4 FIB, 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. The fix corrects this inconsistent behavior so that the error route is respected.
Risk Assessment
Inconsistent routing behavior may lead to traffic being directed to incorrect destinations, potentially causing connectivity or network security issues.
Recommendation
Update the Linux kernel to a version with the fix, and test routing configuration after the update.
Original NVD description (English source)
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.