CyberSecBulletin
CVE-2026-99999NVD status: Received

In the Linux kernel, the following vulnerability has been resolved: ipv4: validate…

Published Updated By the CyberSecBulletin desk

CVE-2026-99999 is a critical-severity improper input validation vulnerability in Linux, with a CVSS 3.1 base score of 9.3 out of 10. It can be exploited with local access to the system by an unauthenticated attacker, without any action from a user. The record lists versions a464d950f31c89565cbaae038cc60db04fe01956, 0fab003ef4698e0628060a45a48f14b43ba2a40a, 94524b7b32691de2e2ce162c04d6cbc9106e5cbf as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.79% chance of exploitation within 30 days, higher than 57% of scored CVEs.

Patch this week

Critical severity: a successful attack would have severe impact.

What to do

  1. Update Linux to a464d950f31c89565cbaae038cc60db04fe01956 or 0fab003ef4698e0628060a45a48f14b43ba2a40a or 94524b7b32691de2e2ce162c04d6cbc9106e5cbf or a65f69e0f38ffbed1b128029e09097436416dc8b, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinuxf43798c27684ab925adde7d8acc34c78c6e50df8 up to, but not including, a464d950f31c89565cbaae038cc60db04fe01956; f43798c27684ab925adde7d8acc34c78c6e50df8 up to, but not including, 0fab003ef4698e0628060a45a48f14b43ba2a40a; f43798c27684ab925adde7d8acc34c78c6e50df8 up to, but not including, 94524b7b32691de2e2ce162c04d6cbc9106e5cbf; f43798c27684ab925adde7d8acc34c78c6e50df8 up to, but not including, a65f69e0f38ffbed1b128029e09097436416dc8b; f43798c27684ab925adde7d8acc34c78c6e50df8 up to, but not including, 32a8b0adaa18e52aaa0b246b5ffe683075354dbb; f43798c27684ab925adde7d8acc34c78c6e50df8 up to, but not including, f3e835af6226f1dd12160cbd696081e9b6155de0; f43798c27684ab925adde7d8acc34c78c6e50df8 up to, but not including, c3e33464746166264334641dc850a36eef7e6326; f43798c27684ab925adde7d8acc34c78c6e50df8 up to, but not including, 6785011f8b16abf40b1e9d8b2e332232b3e68822; and 1 more rangesa464d950f31c89565cbaae038cc60db04fe01956, 0fab003ef4698e0628060a45a48f14b43ba2a40a, 94524b7b32691de2e2ce162c04d6cbc9106e5cbf, a65f69e0f38ffbed1b128029e09097436416dc8b, 32a8b0adaa18e52aaa0b246b5ffe683075354dbb, f3e835af6226f1dd12160cbd696081e9b6155de0

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
LocalThe attacker needs local access or must trick a user into running something.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
NoneNo account or login is needed.
User interaction
NoneNo action by a victim is required.
Scope
ChangedThe attack can reach beyond the vulnerable component into other systems.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H. Scored by CNA.

Official 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.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Improper Input Validation

The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.

How developers prevent this class of flaw

  • Consider using language-theoretic security (LangSec) techniques that characterize inputs using a formal language and build recognizers for that language. This effectively requires parsing to be a distinct layer that effectively enforces a boundary between raw input and internal data representations, instead of allowing parser code to be scattered throughout the program, where it could be subject to errors or inconsistencies that create weaknesses.
  • Use an input validation framework such as Struts or the OWASP ESAPI Validation API. Note that using a framework does not automatically address all input validation problems; be mindful of weaknesses that could arise from misusing the framework itself (CWE-1173).
  • Understand all the potential areas where untrusted inputs can enter the product, including but not limited to: parameters or arguments, cookies, anything read from the network, environment variables, reverse DNS lookups, query results, request headers, URL components, e-mail, files, filenames, databases, and any external systems that provide data to the application. Remember that such inputs may be obtained indirectly through API calls.

More Improper Input Validation vulnerabilities (CWE-20)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
  3. Record last changed materially (score, affected products, status or references).

References

Recent Improper Input Validation vulnerabilities

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