What is CVE-2026-72421?

CVE-2026-72421 is a Critical severity Linux kernel vulnerability with a CVSS score of 10.0 out of 10, affecting Linux kernel versions from 3.6 onward and 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.

What is the CVSS score for CVE-2026-72421?

CVE-2026-72421 has a CVSS score of 10.0 out of 10, rated Critical severity. The vector string is CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N.

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.

Is CVE-2026-72421 actively exploited?

CVE-2026-72421 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.

CVE-2026-72421

Critical

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.

Package Linux Kernel

Published 2026-08-15

Last modified 2026-08-17

CVSS version 3.1

Patch available

Yes

CVSS 3.1 score

10.0

out of 10

Critical

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Changed

Confidentiality

High

Integrity

High

Availability

None

Vector string

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

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 and their respective stable series.

Affected from

≥ 3.6

Fixed in

✓ 5.10.261 5.10.x ✓ 5.15.212 5.15.x ✓ 6.1.178 6.1.x ✓ 6.6.145 6.6.x ✓ 6.12.97 6.12.x ✓ 6.18.40 6.18.x ✓ 7.1.5 7.1.x ✓ 7.2

References

8 total

Showing 5 of 8 references View all on NVD

Details

CVE ID CVE-2026-72421

Severity Critical

CVSS score 10.0 / 10

CVSS version 3.1

Published 2026-08-15

Modified 2026-08-17

KEV No

Patch

Yes

Package linux

Frequently asked questions

What is CVE-2026-72421?

CVE-2026-72421 is a Critical severity Linux kernel vulnerability with a CVSS score of 10.0 out of 10 . 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.
What is the CVSS score for CVE-2026-72421?

CVE-2026-72421 has a CVSS score of 10.0 out of 10, rated Critical severity (CVSS 3.1). The vector string is CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N.
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.
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.