Medium [CVE-2026-64285] Pin source page for write when adding CPUID data for SNP guest
This medium-severity Red Hat Linux advisory covers CVE-2026-64285.
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Summary
In the Linux kernel, the following vulnerability has been resolved: KVM: SEV: Pin source page for write when adding CPUID data for SNP guest When populating a guest_memfd instance with the initial CPUID data for an SNP guest, acquire a writable pin on the source page as KVM will write back the "correct" CPUID information if the userspace provided data is rejected by trusted firmware.
Because KVM writes to the source page using a kernel mapping, pinning for read could result in KVM clobbering read-only memory.
Note, well-behaved VMMs are unlikely to be affected, as CPUID information is almost always dynamically generated by userspace, i.e. it's unlikely for the CPUID information to be backed by a read-only mapping. [sean: rewrite shortlog and changelog, tag for stable@] A flaw was found in the Linux kernel's Kernel-based Virtual Machine (KVM) component, specifically within the Secure Nested Paging (SNP) guest functionality.
When KVM populates a guest's CPUID (Central Processor Unit Identifier) data, it may attempt to write to a source memory page that is intended to be read-only. This incorrect memory pinning could lead to memory corruption, potentially allowing an attacker to overwrite sensitive data within the kernel.
Red Hat severity: Moderate. Weakness: CWE-787.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative. Check it before change work.
Official advisory · medium-confidence parse· fetched 3 days ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists. Confirm against the vendor advisory.
Official advisory · medium-confidence parse· fetched 3 days ago·verify at source
Mitigation
The source record does not include mitigation steps. That does not mean no fix exists. Read the vendor advisory below for the authoritative guidance.
Official advisory · medium-confidence parse· fetched 3 days ago·verify at source
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