AMD SEV Incomplete Cleanup Vulnerability
Summary
A security researcher reported a flaw in VMRUN error handling that may expose Secure Encrypted Virtualization -Secure Nested Paging (SEV-SNP) guest register data to a privileged attacker via a Transient Scheduler Attacks (TSA) side channel attack resulting in a loss of confidentiality. AMD has assessed the report and plans to release mitigations.
CVE Details
Refer to Glossary for explanation of terms
CVE |
CVE Description |
CVSS Base Score |
CVE-2026-40671 |
Incomplete cleanup during VMRUN error handling could allow access to a Secure Encrypted Virtualization-Secure Nested Paging (SEV-SNP) guest register state, potentially resulting in information disclosure and impacts to confidentiality. |
4.9 |
Specific CVSS scores may change subject to your implementation. We encourage you to calculate CVSS scores independently for your system.
Affected Products and Mitigation
AMD plans to release to the Original Equipment Manufacturers (OEM) the Platform Initialization (PI) firmware versions on the target dates listed below. Please contact your OEM for the BIOS update specific to your product(s).
*Note: Products believed to not be affected by the listed CVEs are not included.AMD EPYC™ Series Processors
AMD EPYC™ Series Processors
Product |
CVE ID |
Platform Initialization (PI) Mitigation |
PI Release Date |
Microcode Mitigation |
Microcode Release Date |
AMD EPYC™ 7003 Series Processors |
CVE-2026-40671 |
MilanPI-SP3_1.0.0.L |
Target release planned for Nov'26 |
Milan-B1 0x0A0011E1 Milan-B2 0x0A00124E |
2026-08-12 |
AMD EPYC™ 8004 Series Processors |
CVE-2026-40671 |
Genoa_100J Patch 3 |
Target release planned for Nov'26 |
Siena RSDN - A2 0x0AA0021F | 2026-08-12 |
AMD EPYC™ 8005 Series Processors |
CVE-2026-40671 |
TurinPI_1.0.0.C |
Target release planned for Nov'26 |
0x0B002176 | 2026-08-12 |
AMD EPYC™ 9004 Series Processors |
CVE-2026-40671 |
Genoa_100J Patch 3 |
Target release planned for Nov'26 |
Genoa RS-B1 0x0A10115B Genoa-RS-B2 0x0A10125B |
2026-08-12 |
| Bergamo RSDN-A2 0x0AA0021F | 2026-08-12 |
||||
AMD EPYC™ 9005 Series Processors |
CVE-2026-40671 |
TurinPI_1.0.0.C |
Target release planned for Nov'26 |
Turin Classic -BRH C1 0x0B002176 Turin Dense - BRH D B0 0x0B101067 |
2026-08-12 |
AMD Instinct™ Accelerators
Product |
CVE ID |
Platform Initialization (PI) Mitigation |
PI Release Date |
Microcode Mitigation |
Microcode Release Date |
AMD Instinct™ MI300A Series Processors |
CVE-2026-40671 |
Patch version 0x0A900110 |
2026-09-21 |
0x0A900110 |
2026-09-21 |
AMD EPYC™ Embedded Series Processors
Product |
CVE ID |
Mitigation |
Mitigation Release Date |
AMD EPYC™ Embedded 7003 Series Processors |
CVE-2026-40671 |
Version TBD |
Target release planned for Jan'27 |
AMD EPYC™ Embedded 8004 Series Processors |
CVE-2026-40671 |
Version TBD |
Target release planned for Apr'27 |
AMD EPYC™ Embedded 9004 Series Processors |
CVE-2026-40671 |
Version TBD |
Target release planned for Apr'27 |
AMD EPYC™ Embedded 9005 Series Processors |
CVE-2026-40671 |
Version TBD |
Target release planned for Feb'27 |
Acknowledgement
AMD thanks the following for reporting and engaging in coordinated vulnerability disclosure:
- Alessandro Vezz`u1, Benedict Schluter, Shweta Shinde ETH Zurich, Daniel Moghimi Google: CVE-2026-40671
Revisions
| Revision Date | Description |
| 2026-11-10 | Initial version |
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