CVE-2026-23455Network attack vector

Remote kernel-memory disclosure and crash via H.323 underflow

Published Apr 3, 2026 · Updated Apr 3, 2026

Out-of-bounds read in the H.323 conntrack helper in Linux Kernel allows remote attackers to read kernel memory or crash systems via crafted traffic. DecodeQ931 subtracts one from an unvalidated zero UserUserIE length and passes the wrapped value to DecodeH323_UserInformation. Exposure requires H.323 traffic to traverse a system using nf_conntrack_h323; the resulting over-read exposes kernel memory or interrupts service without modifying data.

CVSS severity9.1
Critical
EPSS probability1.34%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds read in the H.323 conntrack helper in Linux Kernel allows remote attackers to read kernel memory or crash systems via crafted traffic. DecodeQ931 subtracts one from an unvalidated zero UserUserIE length and passes the wrapped value to DecodeH323_UserInformation. Exposure requires H.323 traffic to traverse a system using nf_conntrack_h323; the resulting over-read exposes kernel memory or interrupts service without modifying data.

The record

CVE
CVE-2026-23455
Published
Apr 3, 2026
Updated
Apr 3, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
CWE-125, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 3, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 3, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=2.6.17
  2. Affected versionversion=5e35941d990123f155b02d5663e51a24f816b6f3 <495e97af9e7249ee02b72bb1d0848a6efc3700f4
  3. Affected versionversion=5e35941d990123f155b02d5663e51a24f816b6f3 <633e8f87dad32263f6a57dccdb873f042c062111
  4. Affected versionversion=5e35941d990123f155b02d5663e51a24f816b6f3 <9d00fe7d6d7c5b5f1065a6e042b54f2e44bd6df8
  5. Affected versionversion=5e35941d990123f155b02d5663e51a24f816b6f3 <b652b05d51003ac074b912684f9ec7486231717b
  6. Affected versionversion=5e35941d990123f155b02d5663e51a24f816b6f3 <f173d0f4c0f689173f8cdac79991043a4a89bf66
  7. Affected versionversion=5e35941d990123f155b02d5663e51a24f816b6f3 <f5e4f4e4cdb75ec36802059a94195a31f193da60

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=2.6.17; version=5e35941d990123f155b02d5663e51a24f816b6f3 <495e97af9e7249ee02b72bb1d0848a6efc3700f4; version=5e35941d990123f155b02d5663e51a24f816b6f3 <633e8f87dad32263f6a57dccdb873f042c062111; version=5e35941d990123f155b02d5663e51a24f816b6f3 <9d00fe7d6d7c5b5f1065a6e042b54f2e44bd6df8; version=5e35941d990123f155b02d5663e51a24f816b6f3 <b652b05d51003ac074b912684f9ec7486231717b; version=5e35941d990123f155b02d5663e51a24f816b6f3 <f173d0f4c0f689173f8cdac79991043a4a89bf66; version=5e35941d990123f155b02d5663e51a24f816b6f3 <f5e4f4e4cdb75ec36802059a94195a31f193da60

Published CVSS scores

9.1Linux kernel CVE teamCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
7.0Amazon LinuxCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
7.1OracleCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-125Out-of-bounds Read
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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