Linux Kernel up to 7.1.4 FIB fib_lookup unusual condition

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3.3	$0-$5k	1.01-

Summaryinfo

A vulnerability has been found in Linux Kernel up to 7.1.4 and classified as problematic. Affected by this issue is the function fib_lookup of the component FIB. This manipulation causes unusual condition. This vulnerability is handled as CVE-2026-72421. It is possible to launch the attack on the local host. There is not any exploit available.

Detailsinfo

A vulnerability classified as problematic was found in Linux Kernel up to 7.1.4. Affected by this vulnerability is the function fib_lookup of the component FIB. The manipulation with an unknown input leads to a unusual condition vulnerability. The CWE definition for the vulnerability is CWE-754. The product does not check or incorrectly checks for unusual or exceptional conditions that are not expected to occur frequently during day to day operation of the product. As an impact it is known to affect integrity, and availability. The summary by CVE is:

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.

It is possible to read the advisory at git.kernel.org. This vulnerability is known as CVE-2026-72421 since 08/09/2026. The exploitation appears to be easy. Attacking locally is a requirement. The exploitation needs additional levels of successful authentication. Technical details of the vulnerability are known, but there is no available exploit.

Upgrading to version 5.10.261, 5.15.212, 6.1.178, 6.6.145, 6.12.97, 6.18.40, 7.1.5 or 7.2-rc1 eliminates this vulnerability. Applying the patch a29e95fbc51e8a1b932773fd0e259b2080881443/5ae18d87a45698e8244d0fcba64c658c35a7dd3d/9127589aabdee588278e8d0d0bd3709a760a92c8/49eaf1403201357762d745a35882fb734107d763/fd25996f57a95d56bc568c89b4921edcf334b7d8/828fad4fd418bcdb9f5d66fec0d184c52a85ec31/a668fa160247d7bbe921548cb845f607b8b9305f/b72f0db64205d9ce462038ba995d5d31eff32dc1 is able to eliminate this problem.

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Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 5.10.260
• 5.15.211
• 6.1.177
• 6.6.144
• 6.12.0
• 6.12.1
• 6.12.2
• 6.12.3
• 6.12.4
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• 6.12.90
• 6.12.91
• 6.12.92
• 6.12.93
• 6.12.94
• 6.12.95
• 6.12.96
• 6.18.0
• 6.18.1
• 6.18.2
• 6.18.3
• 6.18.4
• 6.18.5
• 6.18.6
• 6.18.7
• 6.18.8
• 6.18.9
• 6.18.10
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• 6.18.33
• 6.18.34
• 6.18.35
• 6.18.36
• 6.18.37
• 6.18.38
• 6.18.39
• 7.1.0
• 7.1.1
• 7.1.2
• 7.1.3
• 7.1.4

License

• open-source

Website

• Vendor: https://www.kernel.org/

CPE 2.3info

• 🔒
• 🔒
• 🔒

CPE 2.2info

• 🔒
• 🔒
• 🔒

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 3.4
VulDB Meta Temp Score: 3.3

VulDB Base Score: 3.4
VulDB Temp Score: 3.3
VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv2info

AV	AC	Au	C	I	A
💳	💳	💳	💳	💳	💳
💳	💳	💳	💳	💳	💳
💳	💳	💳	💳	💳	💳

Vector	Complexity	Authentication	Confidentiality	Integrity	Availability
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock

VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Unusual condition
CWE: CWE-754
CAPEC: 🔒
ATT&CK: 🔒

Physical: Partially
Local: Yes
Remote: No

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

0-Day	Unlock	Unlock	Unlock	Unlock
Today	Unlock	Unlock	Unlock	Unlock

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Kernel 5.10.261/5.15.212/6.1.178/6.6.145/6.12.97/6.18.40/7.1.5/7.2-rc1
Patch: a29e95fbc51e8a1b932773fd0e259b2080881443/5ae18d87a45698e8244d0fcba64c658c35a7dd3d/9127589aabdee588278e8d0d0bd3709a760a92c8/49eaf1403201357762d745a35882fb734107d763/fd25996f57a95d56bc568c89b4921edcf334b7d8/828fad4fd418bcdb9f5d66fec0d184c52a85ec31/a668fa160247d7bbe921548cb845f607b8b9305f/b72f0db64205d9ce462038ba995d5d31eff32dc1

Timelineinfo

08/09/2026 CVE reserved
08/15/2026 +6 days Advisory disclosed
08/15/2026 +0 days VulDB entry created
08/15/2026 +0 days VulDB entry last update

Sourcesinfo

Vendor: kernel.org

Advisory: git.kernel.org
Status: Confirmed

CVE: CVE-2026-72421 (🔒)
GCVE (CVE): GCVE-0-2026-72421
GCVE (VulDB): GCVE-100-391051

Entryinfo

Created: 08/15/2026 17:17
Changes: 08/15/2026 17:17 (59)
Complete: 🔍
Cache ID: 216::103

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