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VulnerabilityPublished Updated

CVE-2026-43089: Linux kernel · xfrm_user: fix info leak in build_mapping()

Affects Linux kernelSource CVE Database V5

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Not known to be exploited · fixed in f779a6b6cdb6e12baa0663063ac59ab2a8f20c0c : update Linux kernel when convenient.

Data as of 6 Nov 2026, 16:18 UTC

Severity
Medium

Rated Medium by Threat Radar's AI analysis · No CVSS score from NVD or the CNA

Thin evidence

One scorer or none
CISA SSVC
Exploitation
No evidence of active exploitation and no public proof of concept
Automatable
Attackers cannot reliably automate steps 1–4 of the kill chain
Technical impact
Limited control over the software or limited information exposure

CISA SSVC assessment, 2026-11-06.

Patch
Available – fixed in f779a6b6cdb6e12baa0663063ac59ab2a8f20c0c, d3125c541a96fb3c0fc7210112684baf22b6c24d, c2779ae9a3e5a044e5ccd564681511bbbcc5fc0f +5

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 6 May 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 6 Nov 2026.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

ProductAffectedFixed in
LinuxLinuxAffected
  • ≥ 3a2dfbe8acb154905fdc2fd03ec56df42e6c4cc4, < f779a6b6cdb6e12baa0663063ac59ab2a8f20c0c
Fixed in
  • f779a6b6cdb6e12baa0663063ac59ab2a8f20c0c
LinuxLinuxAffected
  • ≥ 3a2dfbe8acb154905fdc2fd03ec56df42e6c4cc4, < d3125c541a96fb3c0fc7210112684baf22b6c24d
Fixed in
  • d3125c541a96fb3c0fc7210112684baf22b6c24d
LinuxLinuxAffected
  • ≥ 3a2dfbe8acb154905fdc2fd03ec56df42e6c4cc4, < c2779ae9a3e5a044e5ccd564681511bbbcc5fc0f
Fixed in
  • c2779ae9a3e5a044e5ccd564681511bbbcc5fc0f
LinuxLinuxAffected
  • ≥ 3a2dfbe8acb154905fdc2fd03ec56df42e6c4cc4, < 521385cbd50ca9474396d88462fcdfa6489685d9
Fixed in
  • 521385cbd50ca9474396d88462fcdfa6489685d9
LinuxLinuxAffected
  • ≥ 3a2dfbe8acb154905fdc2fd03ec56df42e6c4cc4, < 700c9622b23c33b5933e6dcea816492c064e4e10
Fixed in
  • 700c9622b23c33b5933e6dcea816492c064e4e10
LinuxLinuxAffected
  • ≥ 3a2dfbe8acb154905fdc2fd03ec56df42e6c4cc4, < 72a8de41c3eb4dcf22bf3b674ea38fb2f75d6f32
Fixed in
  • 72a8de41c3eb4dcf22bf3b674ea38fb2f75d6f32

AI-suggested

A fix is available and has been applied in the Linux kernel commits identified by the provided fixed version hashes. Users and administrators should update their Linux kernel to a version that includes these fixes to remediate the vulnerability.

Description

CVE-2026-43089 is an information leak vulnerability in the Linux kernel's xfrm_user component. The issue arises because the struct xfrm_usersa_id contains a one-byte padding hole after the proto field that is not zeroed before being copied to userspace. This flaw has been fixed by zeroing the entire structure before setting its fields.

References

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