CVE-2026-64284 Details
Description
In the Linux kernel, the following vulnerability has been resolved: KVM: x86: Ensure vendor's exit handler runs before fastpath userspace exits Move the handling of fastpath userspace exits into vendor code to ensure KVM runs vendor specific operations that need to run before userspace gains control of the vCPU. E.g. for VMX (and soon to be for SVM as well), KVM needs to flush the PML buffer prior to exiting to userspace, otherwise any memory written by the final KVM_RUN might never be flagged as dirty. Note, waiting to snapshot CR0 and CR3 until svm_handle_exit() is flawed in general, as that risks consuming stale state in a fastpath handler. That will be addressed in a future change.
A vulnerability in the Linux kernel's KVM (Kernel-based Virtual Machine) module for x86 architecture has been addressed. The issue involved the handling of fastpath exits to userspace, which was not properly managed within the vendor-specific exit handlers. This could lead to scenarios where critical operations, such as flushing the PML (Page Modification Log) buffer in VMX (Virtual Machine Extensions) mode, were skipped. As a result, memory changes made by the last KVM_RUN command might not be correctly marked as dirty. The vulnerability also posed a risk of capturing outdated state information in fastpath handlers, particularly when waiting to snapshot certain control register values until after handling exits.
Users can upgrade to the latest version of the Linux kernel where this vulnerability has been fixed. Instructions for downloading the patched kernel are available on the official Linux kernel website.
Metrics
CVSS 4.0 Severity and Vector Strings:
No CVSS 4.0 data is available for this CVE.
CVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
No SSVC data is available for this CVE.
References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://git.kernel.org/stable/c/0ffedf43910e44b76c2c1db4e9fbf12b268190c1 | kernel.org | Patch |
| https://git.kernel.org/stable/c/4ad73ef0e7966ecfe67de0060537b4cb14d9acd4 | kernel.org | Patch |
| https://git.kernel.org/stable/c/b3436d9b9b1affe1c3191ac9831308923f5f03c3 | kernel.org | Patch |
| https://git.kernel.org/stable/c/f2ca2b5326211bd38490f0497eb583721ce0bbc0 | kernel.org | Patch |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-367 | Time-of-check Time-of-use (TOCTOU) Race Condition | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| linux linux kernel | >= 6.12, < 6.12.96 >= 6.13, < 6.18.39 >= 6.19, < 7.1.4 |
CPE
Remediation
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Change History
4 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Aug 17, 2026 | CVE Modified | kernel.org |
| Aug 13, 2026 | Initial Analysis | [email protected] |
| Jul 27, 2026 | CVE Modified | kernel.org |
| Jul 25, 2026 | New CVE Received | kernel.org |