Which products and versions are affected by CVE-2026-99999?

Affected: Azl3 Kernel 6.6.157.1-1 (Microsoft); Linux Kernel; Linux (debian) versions >= f43798c27684ab925adde7d8acc34c78c6e50df8, among others. The full list is in the CVE brief.

Is CVE-2026-99999 being exploited in the wild?

It is not listed in any known-exploited vulnerabilities catalog.

Is CVE-2026-99999 in the CISA KEV catalog?

No, it is not currently listed in the CISA Known Exploited Vulnerabilities catalog.

Is there a public exploit for CVE-2026-99999?

No public exploit code is known.

Is there a fix for CVE-2026-99999?

Fixed versions are available, including Kernel 5.10.272, Kernel 5.15.223, Kernel 6.1.190.

How urgently should CVE-2026-99999 be patched?

Brandefense priority: patch in the next maintenance window, because of its high severity, although no exploitation is known.

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Vulnerability Intelligence

CVE-2026-99999

Critical

ipv4: validate checksum_start before completing checksum

Published Oct 15, 2026 · Updated Oct 17, 2026 · Also known as EUVD-2026-102044

Key Facts

Patch in the next maintenance window

CVE-2026-99999 is a critical-severity vulnerability (CVSS 9.3 v3.1) affecting Azl3 Kernel 6.6.157.1-1 (Microsoft), Linux Kernel, Linux (debian) and 1 more product.
It is not listed in any known-exploited vulnerabilities catalog. No public exploit code is known.
EPSS estimates a 0.2% probability of exploitation in the next 30 days.
Fixed versions are available, including Kernel 5.10.272, Kernel 5.15.223, Kernel 6.1.190.
Brandefense priority: patch in the next maintenance window, because of its high severity, although no exploitation is known.

CVSS v3.1

9.3

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

EPSS (30-day exploit likelihood)

0.2%

Higher than 10.6% of all scored CVEs

Exploited in the wild

No known

Not in a known-exploited catalog

Public exploit code

None known

Get the full CVE-2026-99999 brief as a PDF

Every affected product and fixed release, exploitation status and a first 24 hours response checklist, emailed within minutes.

Description

In the Linux kernel, the following vulnerability has been resolved:

ipv4: validate checksum_start before completing checksum

If a packet with bad checksum metadata gets into the ipv4 stack, skb_checksum_help can corrupt the network header and cause a bunch of mischief.

This was discovered and reported by Paulos, and has been reporoduced by others independently since.

We really shouldn't allow such packets in, but as a defence in depth measure, let's also check before we complete the checksum.

A more complete validation at input is forthcoming, but needs more work.

Affected Products

9 affected entries in total

Product	Affected versions	Fixed in
Azl3 Kernel 6.6.157.1-1Microsoft	See advisory	n/a
Linux KernelLinux	See advisory	5.10.272
Linuxdebian	>= f43798c27684ab925adde7d8acc34c78c6e50df8	6.1.190-1
Kernellinux	>= 2.6.27	5.10.272

Patched Releases

Kernel

5.10.272, 5.15.223, 6.1.190, 6.12.113, 6.18.57, 6.6.159, 7.2.11

Linux

6.1.190-1, 6.12.113-1, 7.2.11-1, 0fab003ef4698e0628060a45a48f14b43ba2a40a, 32a8b0adaa18e52aaa0b246b5ffe683075354dbb, 6785011f8b16abf40b1e9d8b2e332232b3e68822, 94524b7b32691de2e2ce162c04d6cbc9106e5cbf, a464d950f31c89565cbaae038cc60db04fe01956, a65f69e0f38ffbed1b128029e09097436416dc8b, c3e33464746166264334641dc850a36eef7e6326, f3e835af6226f1dd12160cbd696081e9b6155de0

Linux Kernel

5.10.272, 5.15.223, 6.1.190, 6.12.113, 6.18.57, 6.6.159, 7.2.11, 7.3-rc7

Timeline

Publicly disclosed
Oct 15, 2026
Last updated
Oct 17, 2026

Weakness Type

CWE-787 Out-of-bounds Write

References

10 more references in the full CVE brief

FAQ

Common Questions.

In the Linux kernel, the following vulnerability has been resolved: ipv4: validate checksum_start before completing checksum If a packet with bad checksum metadata gets into the ipv4 stack, skb_checksum_help can corrupt the network header and cause a bunch of mischief.
Affected: Azl3 Kernel 6.6.157.1-1 (Microsoft); Linux Kernel; Linux (debian) versions >= f43798c27684ab925adde7d8acc34c78c6e50df8, among others. The full list is in the CVE brief.
It is not listed in any known-exploited vulnerabilities catalog.
No, it is not currently listed in the CISA Known Exploited Vulnerabilities catalog.
No public exploit code is known.
Fixed versions are available, including Kernel 5.10.272, Kernel 5.15.223, Kernel 6.1.190.
Brandefense priority: patch in the next maintenance window, because of its high severity, although no exploitation is known.

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