ipv4: fib: Don't ignore error route in local/main tables.
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- —
- Confidentiality · integrity · availability
- High · High · None
- Fix status
- Partial Red Hat: 5 without a fix
Attack profile from CVSS 3.1 · CNA. Fix status from CNA and Red Hat.
Summary
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.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- Yes
- Technical impact
- Total
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
Remediation
- Fix · CNA Linux (Linux) 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
Vendor assessments
Red Hat
Red Hat rating: Low. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat Enterprise Linux 10 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 6 | Affected | No fix planned: Out of support scope |
| Red Hat Enterprise Linux 7 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 8 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 9 | Affected | No fix yet: Fix deferred |
Timeline
- 2026-10-02 Threatist record created from CVE-2026-72421
- 2026-10-03 Alias added: GHSA-66j4-c66h-jm7x
- 2026-10-16 CISA SSVC decision points changed
References
Other 8
- 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
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- TI-2022-00125 Integer overflow in kernel KEVCVSS 3.1HIGH 8.4
- TI-2013-01864 The perf_swevent_init function in kernel/events/core.c in the Linux kernel before 3.8.9… KEVCVSS 3.1HIGH 8.4
Sources
- CVE-2026-72421 · CVE Program
- CVE-2026-72421 · NVD
- FIRST EPSS
- GHSA-66j4-c66h-jm7x · GitHub Advisory Database · CC BY 4.0
- CVE-2026-72421 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences