What’s Vulnerable › Vulnerabilities

CVE-2021-46977: KVM: VMX: Disable preemption when probing user return MSRs

• Severity: medium (CVSS 5.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2024-02-28 · updated 2026-08-04

Description

In the Linux kernel, the following vulnerability has been resolved: KVM: VMX: Disable preemption when probing user return MSRs Disable preemption when probing a user return MSR via RDSMR/WRMSR. If the MSR holds a different value per logical CPU, the WRMSR could corrupt the host's value if KVM is preempted between the RDMSR and WRMSR, and then rescheduled on a different CPU. Opportunistically land the helper in common x86, SVM will use the helper in a future commit.

Affected products

• Linux kernel: from 5.5 before 5.10.38; from 5.11 before 5.11.22; from 5.12 before 5.12.5; 5.13-rc1 — fixed in 5.10.38, 5.11.22, 5.12.5

How to fix

Upgrade to a fixed version: Linux kernel 5.10.38, 5.11.22, 5.12.5. Check the vendor advisory for mitigations.

References

• https://git.kernel.org/stable/c/31f29749ee970c251b3a7e5b914108425940d089
• https://git.kernel.org/stable/c/5104d7ffcf24749939bea7fdb5378d186473f890
• https://git.kernel.org/stable/c/5adcdeb57007ccf8ab7ac20bf787ffb6fafb1a94
• https://git.kernel.org/stable/c/e3ea1895df719c4ef87862501bb10d95f4177bed
• https://git.kernel.org/stable/c/31f29749ee970c251b3a7e5b914108425940d089
• https://git.kernel.org/stable/c/5104d7ffcf24749939bea7fdb5378d186473f890
• https://git.kernel.org/stable/c/5adcdeb57007ccf8ab7ac20bf787ffb6fafb1a94
• https://git.kernel.org/stable/c/e3ea1895df719c4ef87862501bb10d95f4177bed

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