# 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.

- Page: https://www.vulneraibility.com/cve/CVE-2026-99999
- CVSS: 9.3
- Known exploited: not in CISA KEV as of our last sync
- EPSS: 0.79% (percentile 56.7)
- Unvetted proof-of-concept code on GitHub: 14 GitHub proofs of concept (first 2026-10-16)
- CISA SSVC: exploitation none, automatable no, technical impact total (assessed 2026-10-16)
- Weakness: CWE-20
- Published: 2026-10-15

## Affected versions

- Linux: affected >= f43798c27684ab925adde7d8acc34c78c6e50df8 and < a464d950f31c89565cbaae038cc60db04fe01956; >= f43798c27684ab925adde7d8acc34c78c6e50df8 and < 0fab003ef4698e0628060a45a48f14b43ba2a40a; >= f43798c27684ab925adde7d8acc34c78c6e50df8 and < 94524b7b32691de2e2ce162c04d6cbc9106e5cbf; >= f43798c27684ab925adde7d8acc34c78c6e50df8 and < a65f69e0f38ffbed1b128029e09097436416dc8b; >= f43798c27684ab925adde7d8acc34c78c6e50df8 and < 32a8b0adaa18e52aaa0b246b5ffe683075354dbb; >= f43798c27684ab925adde7d8acc34c78c6e50df8 and < f3e835af6226f1dd12160cbd696081e9b6155de0; >= f43798c27684ab925adde7d8acc34c78c6e50df8 and < c3e33464746166264334641dc850a36eef7e6326; >= f43798c27684ab925adde7d8acc34c78c6e50df8 and < 6785011f8b16abf40b1e9d8b2e332232b3e68822; 2.6.27; fixed in < 2.6.27, >= 5.10.272 and <= 5.10.*, >= 5.15.223 and <= 5.15.*, >= 6.1.190 and <= 6.1.*, >= 6.6.159 and <= 6.6.*, >= 6.12.113 and <= 6.12.*, >= 6.18.57 and <= 6.18.*, >= 7.2.11 and <= 7.2.*, >= 7.3 and <= *

A version outside these ranges is not a statement that it is unaffected.

## References

- [other] https://git.kernel.org/stable/c/a464d950f31c89565cbaae038cc60db04fe01956
- [other] https://git.kernel.org/stable/c/0fab003ef4698e0628060a45a48f14b43ba2a40a
- [other] https://git.kernel.org/stable/c/94524b7b32691de2e2ce162c04d6cbc9106e5cbf
- [other] https://git.kernel.org/stable/c/a65f69e0f38ffbed1b128029e09097436416dc8b
- [other] https://git.kernel.org/stable/c/32a8b0adaa18e52aaa0b246b5ffe683075354dbb
- [other] https://git.kernel.org/stable/c/f3e835af6226f1dd12160cbd696081e9b6155de0
- [other] https://git.kernel.org/stable/c/c3e33464746166264334641dc850a36eef7e6326
- [other] https://git.kernel.org/stable/c/6785011f8b16abf40b1e9d8b2e332232b3e68822
- [other] https://pwn.ai/blog/pwnescape
- [other] https://vercel.com/blog/findings-from-the-1-million-dollar-vercel-sandbox-challenge
- [other] http://www.openwall.com/lists/oss-security/2026/10/15/5

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Summary, impact and action are written by the vulneraibility.com AI analysis pipeline from the CVE record, NVD, CISA and FIRST data; verify against the references.