CVE-2026-23440Network attack vector

IPsec traffic halt via duplicate ESN processing

Published Apr 3, 2026 · Updated Apr 3, 2026

Race condition in affected Linux Kernel mlx5e IPsec full-offload code allows remote attackers to halt IPsec traffic. The ESN event handler calls mlx5_accel_esp_modify_xfrm() before re-arming esn_event_arm, so a duplicate event can increment esn_msb twice and program invalid hardware state. Reachability requires an active mlx5 IPsec full-offload security association and enough peer traffic to drive an ESN event; the resulting anti-replay failures stop that IPsec traffic without reported data disclosure or modification.

CVSS severity7.5
High
EPSS probability0.21%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Race condition in affected Linux Kernel mlx5e IPsec full-offload code allows remote attackers to halt IPsec traffic. The ESN event handler calls mlx5_accel_esp_modify_xfrm() before re-arming esn_event_arm, so a duplicate event can increment esn_msb twice and program invalid hardware state. Reachability requires an active mlx5 IPsec full-offload security association and enough peer traffic to drive an ESN event; the resulting anti-replay failures stop that IPsec traffic without reported data disclosure or modification.

The record

CVE
CVE-2026-23440
Published
Apr 3, 2026
Updated
Apr 3, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
CWE-362, T1499.004
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

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Is a vulnerable build present?

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

  1. Affected versionversion=6.4
  2. Affected versionversion=fef06678931ff67b158d337b581e5cf5ca40a3a3 <2051c709dce92da3550040aa7949cd5a9c89b14e
  3. Affected versionversion=fef06678931ff67b158d337b581e5cf5ca40a3a3 <3dffc083292e6872787bd7e34b957627622f9af4
  4. Affected versionversion=fef06678931ff67b158d337b581e5cf5ca40a3a3 <8d625c15471fb8780125eaef682983a96af77bdc
  5. Affected versionversion=fef06678931ff67b158d337b581e5cf5ca40a3a3 <96c9c25b74686ac2de15921c9ad30c5ef13af8cd
  6. Affected versionversion=fef06678931ff67b158d337b581e5cf5ca40a3a3 <beb6e2e5976a128b0cccf10d158124422210c5ef

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=6.4; version=fef06678931ff67b158d337b581e5cf5ca40a3a3 <2051c709dce92da3550040aa7949cd5a9c89b14e; version=fef06678931ff67b158d337b581e5cf5ca40a3a3 <3dffc083292e6872787bd7e34b957627622f9af4; version=fef06678931ff67b158d337b581e5cf5ca40a3a3 <8d625c15471fb8780125eaef682983a96af77bdc; version=fef06678931ff67b158d337b581e5cf5ca40a3a3 <96c9c25b74686ac2de15921c9ad30c5ef13af8cd; version=fef06678931ff67b158d337b581e5cf5ca40a3a3 <beb6e2e5976a128b0cccf10d158124422210c5ef

Published CVSS scores

7.5kernel.orgCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
4.7NIST NVDCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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-362Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
T1499.004Application or System Exploitation

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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