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VulnerabilityPublished Updated

CVE-2026-68166: Linux kernel · userfaultfd: prevent registration of special VMAs

Affects Linux kernelSource CVE Database V5

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Not known to be exploited · fixed in d974b4b786214883bd8e56bda10b454c80fd6205 : patch Linux kernel soon.

Data as of 6 Nov 2026, 17:19 UTC

Severity
High

Rated High 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 d974b4b786214883bd8e56bda10b454c80fd6205, 165613191ad9d034bf17c00e3a142f9561597ec5, 495a28d5a100be1b232633f4c2dcc42ba10b3796 +2

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 10 Aug 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
  • ≥ 54007f818206dc27309ca423df4c87dd160a7208, < d974b4b786214883bd8e56bda10b454c80fd6205
Fixed in
  • d974b4b786214883bd8e56bda10b454c80fd6205
LinuxLinuxAffected
  • ≥ 54007f818206dc27309ca423df4c87dd160a7208, < 165613191ad9d034bf17c00e3a142f9561597ec5
Fixed in
  • 165613191ad9d034bf17c00e3a142f9561597ec5
LinuxLinuxAffected
  • ≥ 54007f818206dc27309ca423df4c87dd160a7208, < 495a28d5a100be1b232633f4c2dcc42ba10b3796
Fixed in
  • 495a28d5a100be1b232633f4c2dcc42ba10b3796
LinuxLinuxAffected
  • ≥ 54007f818206dc27309ca423df4c87dd160a7208, < 3c58f641e813c3c71039f8fd4d4e2a3aab713288
Fixed in
  • 3c58f641e813c3c71039f8fd4d4e2a3aab713288
LinuxLinuxAffected
  • ≥ 54007f818206dc27309ca423df4c87dd160a7208, < 0c26202b157f1efc3cd2f26f5c30f59b508a6a5d
Fixed in
  • 0c26202b157f1efc3cd2f26f5c30f59b508a6a5d
LinuxLinuxAffected
  • =6.6
Fixed in–

AI-suggested

This vulnerability is fixed in Linux kernel version 6.6 and later. Users and administrators should update to version 6.6 or apply the corresponding patches to prevent exploitation. No additional mitigation steps are required beyond applying the official fix.

Description

A vulnerability in the Linux kernel's userfaultfd interface allowed registration on special virtual memory areas (VMAs), including shadow stack VMAs. This could enable an attacker with userfaultfd access to manipulate shadow stack pages and inject arbitrary return addresses. The issue has been fixed by updating the kernel to reject registration on VM_SHADOW_STACK and VM_SPECIAL VMAs, preventing such misuse.

References

Community reviews

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