9.3

CVE-2026-99999: ipv4: validate checksum_start before completing checksum

Received
AliasesDEBIAN-CVE-2026-99999UBUNTU-CVE-2026-99999
Published 15-10-2026Last modified 24-10-2026

Vulnerability summary

CVE-2026-99999 is a critical (CVSS 9.3) Improper Input Validation vulnerability in linux. EPSS estimates a 0.79% chance of exploitation in the next 30 days, higher than 56.2% of scored vulnerabilities.

Priority
Prioritisesevere

Severe, CVSS 9.3 (CVE.org); no exploitation reported by the 5 checked sources; EPSS 1% (FIRST, 03-11-2026)

Source freshness unavailable

How is this decided?
CVSS score
9.3/10
010
Critical · v3.1 (CVE.org)
EPSS score
0.79%
0%100%
Low · Change unavailable
KEVNot listedNot listed by any tracked catalog.
RansomwareNot flaggedNo ransomware use recorded.
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 16 · Related 16
OPENSUSE-SU-2026:22167-1SUSE-SU-2026:24371-1SUSE-SU-2026:24379-1SUSE-SU-2026:24386-1SUSE-SU-2026:24422-1SUSE-SU-2026:24437-1

Timeline

  1. 15-10-2026
    PublishedVulnerability first disclosed.
  2. 24-10-2026
    Last modifiedVulnerability information updated.

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.

CVSS metrics

5 scores · 4 sources · 2 versions

EPSS trend

Probability

0.79%

Chance of exploitation in the next 30 days

Percentile

56%

Versus all other CVEs

30-day change

Change unavailable

Change unavailable

16-10-202603-11-2026

Known exploited

Compare KEV catalogs
CISA KEV

Not in the CISA KEV catalog.

ENISA CNW

Not in the ENISA CNW catalog.

CIRCL

Not in the CIRCL catalog.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Version check

Known conditions: local access, no authentication, no user interaction (CVSS vector). Other conditions: not stated in public data.

Ubuntu169 products
  • linuxAll versions (No fix recorded)
  • linux-allwinner-5.19All versions (No fix recorded)
  • linux-awsAll versions (No fix recorded)
  • linux-aws-5.0All versions (No fix recorded)
  • linux-aws-5.11All versions (No fix recorded)
Debian2 products
  • linuxAll versions (No fix recorded) | < 6.1.190-1 | < 6.12.113-1 | < 7.2.11-1
  • linux-6.12< 6.12.113-1~deb12u1
Linux1 product
  • linux≥ f43798c27684ab925adde7d8acc34c78c6e50df8, < a464d950f31c89565cbaae038cc60db04fe01956 | ≥ f43798c27684ab925adde7d8acc34c78c6e50df8, < 0fab003ef4698e0628060a45a48f14b43ba2a40a | ≥ f43798c27684ab925adde7d8acc34c78c6e50df8, < 94524b7b32691de2e2ce162c04d6cbc9106e5cbf | ≥ f43798c27684ab925adde7d8acc34c78c6e50df8, < a65f69e0f38ffbed1b128029e09097436416dc8b | ≥ f43798c27684ab925adde7d8acc34c78c6e50df8, < 32a8b0adaa18e52aaa0b246b5ffe683075354dbb | ≥ f43798c27684ab925adde7d8acc34c78c6e50df8, < f3e835af6226f1dd12160cbd696081e9b6155de0 | ≥ f43798c27684ab925adde7d8acc34c78c6e50df8, < c3e33464746166264334641dc850a36eef7e6326 | ≥ f43798c27684ab925adde7d8acc34c78c6e50df8, < 6785011f8b16abf40b1e9d8b2e332232b3e68822 | 2.6.27

3 vendors · 172 products

References

16 links
Show all 16 references