{"cve":"CVE-2025-38508","nvd":{"published":"2025-08-16T11:15:43.773","modified":"2026-07-30T06:23:23.177","status":"Modified","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nx86/sev: Use TSC_FACTOR for Secure TSC frequency calculation\n\nWhen using Secure TSC, the GUEST_TSC_FREQ MSR reports a frequency based on\nthe nominal P0 frequency, which deviates slightly (typically ~0.2%) from\nthe actual mean TSC frequency due to clocking parameters.\n\nOver extended VM uptime, this discrepancy accumulates, causing clock skew\nbetween the hypervisor and a SEV-SNP VM, leading to early timer interrupts as\nperceived by the guest.\n\nThe guest kernel relies on the reported nominal frequency for TSC-based\ntimekeeping, while the actual frequency set during SNP_LAUNCH_START may\ndiffer. This mismatch results in inaccurate time calculations, causing the\nguest to perceive hrtimers as firing earlier than expected.\n\nUtilize the TSC_FACTOR from the SEV firmware's secrets page (see \"Secrets\nPage Format\" in the SNP Firmware ABI Specification) to calculate the mean\nTSC frequency, ensuring accurate timekeeping and mitigating clock skew in\nSEV-SNP VMs.\n\nUse early_ioremap_encrypted() to map the secrets page as\nioremap_encrypted() uses kmalloc() which is not available during early TSC\ninitialization and causes a panic.\n\n  [ bp: Drop the silly dummy var:\n    https://lore.kernel.org/r/20250630192726.GBaGLlHl84xIopx4Pt@fat_crate.local ]","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","score":5.5},"cwes":[],"references":["https://git.kernel.org/stable/c/52e1a03e6cf61ae165f59f41c44394a653a0a788","https://git.kernel.org/stable/c/d0195c42e65805938c9eb507657e7cdf8e1e9522"],"products":["linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-19T22:06:45.861874017+00:00"},"epss":{"cve":"CVE-2025-38508","score":0.00131,"percentile":0.0265,"date":"2026-10-31"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}