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VulnerabilityPublished Updated

CVE-2026-31561: Linux kernel · x86/cpu: Remove X86_CR4_FRED from the CR4 pinned bits mask

Affects Linux kernelSource GCVE Database

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Not known to be exploited.

Data as of 12 Nov 2026, 03:33 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

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 11 Nov 2026.

What to do

AI-suggested

A fix has been implemented in the Linux kernel that removes the X86_CR4_FRED bit from the CR4 pinned bits mask, eliminating the need to disable CR4 pinning temporarily. Users should update to the fixed kernel version once available. No other mitigation steps are indicated or necessary as the patch addresses the root cause directly.

Description

A vulnerability in the Linux kernel related to the handling of the X86_CR4_FRED bit in the CR4 pinned bits mask has been resolved. The issue involved a timing window during system boot where exceptions could not be handled properly, especially affecting SEV-ES, SEV-SNP, and TDX guests, potentially causing triple faults. The fix removes the FRED bit from the CR4 pinning mask to prevent disabling CR4 pinning temporarily, which could be exploited by attackers to disable security features and compromise the system.

References

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