CVE-2025-38508: Linux kernel · x86/sev: Use TSC_FACTOR for Secure TSC frequency calculation
Source GCVE Database
Not known to be exploited · CVSS 5.5 Medium.
Data as of 13 Nov 2026, 18:29 UTC
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:HExploitation evidence
Disclosed: evidence found.
CVE published 16 Aug 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by 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 13 Nov 2026.
Description
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 ]