CVE-2026-43089

Kernel-memory disclosure via uninitialized mapping padding

Published May 6, 2026 · Updated May 6, 2026

Information disclosure in affected Linux Kernel releases allows local users to read one uninitialized kernel-memory byte via XFRM netlink. The build_mapping() function fills struct xfrm_usersa_id fields without clearing the one-byte padding hole after proto, then copies the whole structure into an XFRM mapping notification. Reachability requires an ESP UDP-encapsulation mapping notification in the relevant network namespace, and each notification exposes only that padding byte.

CVSS severity5.5
Medium
EPSS probability0.13%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Information disclosure in affected Linux Kernel releases allows local users to read one uninitialized kernel-memory byte via XFRM netlink. The build_mapping() function fills struct xfrm_usersa_id fields without clearing the one-byte padding hole after proto, then copies the whole structure into an XFRM mapping notification. Reachability requires an ESP UDP-encapsulation mapping notification in the relevant network namespace, and each notification exposes only that padding byte.

The record

CVE
CVE-2026-43089
Published
May 6, 2026
Updated
May 6, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
CWE-401
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. May 6, 2026CVE publishedPublication date reported by the CVE source.
  2. May 6, 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=2.6.29
  2. Affected versionversion=3a2dfbe8acb154905fdc2fd03ec56df42e6c4cc4 <1beb76b2053b68c491b78370794b8ff63c8f8c02
  3. Affected versionversion=3a2dfbe8acb154905fdc2fd03ec56df42e6c4cc4 <5a1a4b049ddde41466ccac0daeec326254b133f2
  4. Affected versionversion=3a2dfbe8acb154905fdc2fd03ec56df42e6c4cc4 <700c9622b23c33b5933e6dcea816492c064e4e10
  5. Affected versionversion=3a2dfbe8acb154905fdc2fd03ec56df42e6c4cc4 <d3125c541a96fb3c0fc7210112684baf22b6c24d
  6. Affected versionversion=3a2dfbe8acb154905fdc2fd03ec56df42e6c4cc4 <f779a6b6cdb6e12baa0663063ac59ab2a8f20c0c

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=2.6.29; version=3a2dfbe8acb154905fdc2fd03ec56df42e6c4cc4 <1beb76b2053b68c491b78370794b8ff63c8f8c02; version=3a2dfbe8acb154905fdc2fd03ec56df42e6c4cc4 <5a1a4b049ddde41466ccac0daeec326254b133f2; version=3a2dfbe8acb154905fdc2fd03ec56df42e6c4cc4 <700c9622b23c33b5933e6dcea816492c064e4e10; version=3a2dfbe8acb154905fdc2fd03ec56df42e6c4cc4 <d3125c541a96fb3c0fc7210112684baf22b6c24d; version=3a2dfbe8acb154905fdc2fd03ec56df42e6c4cc4 <f779a6b6cdb6e12baa0663063ac59ab2a8f20c0c

Published CVSS scores

5.5NIST NVDCVSS:3.1/AV:L/AC:L/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.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-401Missing Release of Memory after Effective Lifetime

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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