CVE intelligence

CVE-2026-99999

Vulnerability intelligence

Published Oct 15, 2026Sources checked Oct 21, 2026

9.3CRITICALCVSS out of 10

What this means

Review the available evidence

CVE-2026-99999 and is rated Critical severity with a CVSS score of 9.3. It is not in the current CISA KEV record we collected. That does not prove exploitation has not occurred.

What to do next

Remediation and response

Microsoft Security Response Center guidance

Vendor revision: Oct 21, 2026

Release Notes

Vendor-listed releases

6.6.159.1-1

CISA KEVNot listedBased on the latest collected catalog

EPSS0.2%Estimated 30-day exploitation probability

Ransomware useNot markedCISA KEV ransomware field

Threat actors0Source-linked actor relationships

Overview

What is CVE-2026-99999?

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.

Source: NVD