CVE-2026-31575: Linux kernel · mm/userfaultfd: fix hugetlb fault mutex hash calculation
Affects Linux kernelSource CVE Database V5
Not known to be exploited · fixed in f4689fc089765d36c026063fb22d23533e883eb6 : patch Linux kernel soon.
Data as of 5 Nov 2026, 22:05 UTC
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
Disclosed: evidence found.
CVE published 24 Apr 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by 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
| Product | Affected | Fixed in |
|---|---|---|
| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| 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
- git.kernel.org/stable/c/5a525c43baaba0bf3063f86996ca3623b71e4172 (opens in a new tab)
- git.kernel.org/stable/c/574501ede47ac439afd67ba9812bc66722d500ba (opens in a new tab)
- git.kernel.org/stable/c/08282b1bf74c69fc8ecd25493e7fdb5460f01290 (opens in a new tab)
- git.kernel.org/stable/c/f4689fc089765d36c026063fb22d23533e883eb6 (opens in a new tab)
- git.kernel.org/stable/c/0217c7fb4de4a40cee667eb21901f3204effe5ac (opens in a new tab)