CVE-2025-38508

What it is

In the Linux kernel, the following vulnerability has been resolved: x86/sev: Use TSC_FACTOR for Secure TSC frequency calculation When using Secure TSC, the GUEST_TSC_FREQ MSR reports a frequency based on the nominal P0 frequency, which deviates slightly (typically ~0.2%) from the actual mean TSC frequency due to clocking parameters. Over extended VM uptime, this discrepancy accumulates, causing clock skew between the hypervisor and a SEV-SNP VM, leading to early timer interrupts as perceived by the guest. The guest kernel relies on the reported nominal frequency for TSC-based timekeeping, while the actual frequency set during SNP_LAUNCH_START may differ. This mismatch results in inaccurate time calculations, causing the guest to perceive hrtimers as firing earlier than expected. Utilize the TSC_FACTOR from the SEV firmware's secrets page (see "Secrets Page Format" in the SNP Firmware ABI Specification) to calculate the mean TSC frequency, ensuring accurate timekeeping and mitigating clock skew in SEV-SNP VMs. Use early_ioremap_encrypted() to map the secrets page as ioremap_encrypted() uses kmalloc() which is not available during early TSC initialization and causes a panic. [ bp: Drop the silly dummy var: https://lore.kernel.org/r/20250630192726.GBaGLlHl84xIopx4Pt@fat_crate.local ]

At a glance

Exploitability

Can be exploited locally on the machine without logging in. High risk of service disruption.

Exploit odds

0.1% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2025-08-16 11:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-07-30 06:23 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.1% in the next 30 days (EPSS).
• Severity: 7.3 HIGH (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2025-08-16 11:15 UTC

Last modified

2026-07-30 06:23 UTC

Exploit probability

0.1% · EPSS, next 30 days

Record status

Modified

Affected

• Linux Kernel < 6.15.7
• Linux Kernel 6.16

Attack profile CVSS 3.1 · 7.3

Attack vector

Local

Complexity

Low

Privileges needed

None

User interaction

None

Scope

Unchanged

Confidentiality

Low

Integrity

Low

Availability

High

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2025-38508.md and follow it. Check whether this project is affected by CVE-2025-38508. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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