CVE-2026-99999critical

CVE-2026-99999: critical vulnerability in Linux

ipv4: validate checksum_start before completing checksum

Published · Updated

48Vexday Risk Score

No sign of exploitation. It has a public proof of concept.

ssvc Attendcvss 9.3epss 0.2%
from disclosure to weapon1 days
Published on NVDOct 15
1st PoC+1d
exploitation probability
0.2%top 89% of all CVEs
observed exploitation
nono source reports it
3 public exploit(s)
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:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
Affected products
Linux · Linux
public PoCs found — 3
githubgithub.com/MChorfa/csumguard★ 1githubgithub.com/PeronGH/CVE-2026-99999★ 1githubgithub.com/Quaerendir/cve-2026-99999-audit★ 0
⚠ Public resources, to assess the exposure of systems you control or are authorized to test. Test only with authorization.
Related CVEs — Linux

In the same product, most dangerous first.

CVE-2024-53197HIGHALSA: usb-audio: Fix potential out-of-bound accesses for Extigy and Mbox devicesEPSS 4.1%KEVCVE-2026-31431HIGHcrypto: algif_aead - Revert to operating out-of-placeEPSS 3.4%KEVCVE-2024-53104HIGHmedia: uvcvideo: Skip parsing frames of type UVC_VS_UNDEFINED in uvc_parse_formatEPSS 3.4%KEVCVE-2025-39682CRITICALtls: fix handling of zero-length records on the rx_listEPSS 2.9%KEVCVE-2024-36971HIGHnet: fix __dst_negative_advice() raceEPSS 2.7%KEVCVE-2025-39964HIGHcrypto: af_alg - Disallow concurrent writes in af_alg_sendmsgEPSS 1.4%KEV
References
https://git.kernel.org/stable/c/0fab003ef4698e0628060a45a48f14b43ba2a40ahttps://git.kernel.org/stable/c/32a8b0adaa18e52aaa0b246b5ffe683075354dbbhttps://git.kernel.org/stable/c/6785011f8b16abf40b1e9d8b2e332232b3e68822https://git.kernel.org/stable/c/94524b7b32691de2e2ce162c04d6cbc9106e5cbfhttps://git.kernel.org/stable/c/a464d950f31c89565cbaae038cc60db04fe01956https://git.kernel.org/stable/c/a65f69e0f38ffbed1b128029e09097436416dc8bhttps://git.kernel.org/stable/c/c3e33464746166264334641dc850a36eef7e6326https://git.kernel.org/stable/c/f3e835af6226f1dd12160cbd696081e9b6155de0https://pwn.ai/blog/pwnescapehttps://vercel.com/blog/findings-from-the-1-million-dollar-vercel-sandbox-challengehttp://www.openwall.com/lists/oss-security/2026/10/15/5