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VulnerabilityPublished Updated

CVE-2026-31575: Linux kernel · mm/userfaultfd: fix hugetlb fault mutex hash calculation

Affects Linux kernelSource CVE Database V5

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Not known to be exploited · fixed in f4689fc089765d36c026063fb22d23533e883eb6 : patch Linux kernel soon.

Data as of 5 Nov 2026, 22:05 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, 2026-11-05.

Patch
Available – fixed in f4689fc089765d36c026063fb22d23533e883eb6, 574501ede47ac439afd67ba9812bc66722d500ba, 08282b1bf74c69fc8ecd25493e7fdb5460f01290 +2

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 24 Apr 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 5 Nov 2026.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

ProductAffectedFixed in
LinuxLinuxAffected
  • ≥ a08c7193e4f18dc8508f2d07d0de2c5b94cb39a3, < f4689fc089765d36c026063fb22d23533e883eb6
Fixed in
  • f4689fc089765d36c026063fb22d23533e883eb6
LinuxLinuxAffected
  • ≥ a08c7193e4f18dc8508f2d07d0de2c5b94cb39a3, < 574501ede47ac439afd67ba9812bc66722d500ba
Fixed in
  • 574501ede47ac439afd67ba9812bc66722d500ba
LinuxLinuxAffected
  • ≥ a08c7193e4f18dc8508f2d07d0de2c5b94cb39a3, < 08282b1bf74c69fc8ecd25493e7fdb5460f01290
Fixed in
  • 08282b1bf74c69fc8ecd25493e7fdb5460f01290
LinuxLinuxAffected
  • ≥ a08c7193e4f18dc8508f2d07d0de2c5b94cb39a3, < 0217c7fb4de4a40cee667eb21901f3204effe5ac
Fixed in
  • 0217c7fb4de4a40cee667eb21901f3204effe5ac
LinuxLinuxAffected
  • ≥ a08c7193e4f18dc8508f2d07d0de2c5b94cb39a3, < 5a525c43baaba0bf3063f86996ca3623b71e4172
Fixed in
  • 5a525c43baaba0bf3063f86996ca3623b71e4172
LinuxLinuxAffected
  • =6.7
Fixed in–

AI-suggested

A fix is available and has been applied in the Linux kernel. Users should update to the fixed kernel versions identified by the commits f4689fc089765d36c026063fb22d23533e883eb6, 574501ede47ac439afd67ba9812bc66722d500ba, 08282b1bf74c69fc8ecd25493e7fdb5460f01290, 0217c7fb4de4a40cee667eb21901f3204effe5ac, and 5a525c43baaba0bf3063f86996ca3623b71e4172. No additional mitigation steps are indicated.

Description

A vulnerability in the Linux kernel's userfaultfd subsystem related to hugetlb fault mutex hash calculation has been fixed. The issue was caused by a mismatch in page index units used in hashing, leading to different mutexes being used for the same huge page. This could cause race conditions between faulting threads, potentially corrupting the reservation map and triggering kernel errors. The fix introduces a new function to correctly calculate the page index in huge page granularity.

References

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