Undermining Integrity Features of SEV-SNP with Memory Aliasing
AMD ID: AMD-SB-3015
Potential Impact: Loss of Integrity
Severity: Medium
Summary
A team of researchers has reported to AMD that it may be possible to modify serial presence detect (SPD) metadata to make an attached memory module appear larger than it is, potentially allowing an attacker to overwrite physical memory.
CVE Details
Refer to Glossary for explanation of terms
CVE |
CVSS Score |
CVE Description |
CVE-2024-21944 |
5.3 (Medium) AV:L/AC:H/PR:H/UI:N/S:C/C:N/I:H/A:N |
Improper input validation for DIMM serial presence detect (SPD) metadata could allow an attacker with physical access, ring0 access on a system with a non-compliant DIMM, or control over the Root of Trust for BIOS update, to potentially overwrite guest memory resulting in loss of guest data integrity. |
Affected Products by CVE
Data Center
3rd Gen AMD EPYC™ Processors formerly codenamed “Milan”
3rd Gen AMD EPYC™ Processors formerly codenamed “Milan-X”
4th Gen AMD EPYC™ Processors formerly codenamed “Genoa”
4th Gen AMD EPYC™ Processors formerly codenamed “Bergamo”
4th Gen AMD EPYC™ Processors formerly codenamed “Genoa-X”
4th Gen AMD EPYC™ Processors formerly codenamed “Siena”
Mitigation
AMD recommends utilizing memory modules that lock SPD, as well as following physical security best practices. In addition, the AGESA™ and SEV FW versions listed below have been released to the Original Equipment Manufacturers (OEM) to mitigate this issue. Please refer to your OEM for the BIOS update specific to your product.
There is specific status information that is provided and available for a Host OS / Hypervisor, and also available for a Virtual Machine (Guest) to indicate that the mitigation has been deployed.
Please refer to ABI Specification 56860 for the Guest attestation and Platform Status commands containing information regarding deployment for the mitigations.
Please Note: The below ATTESTATION_REPORT Structure and STRUCT_PLATFORM_STATUS Structure commands are part of the ABI spec and will part of the ABI Specification publication post AMD-SB-3015 embargo.
SEV FW versions in Mitigation sections of 3rd Gen AMD EPYC™ and 4th Gen AMD EPYC™ Processors contains the ALIAS_CHECK mitigation reporting as described below:
Guest Attestation Report [Attestation method for Guest VM]
ATTESTATION_REPORT Structure PLATFORM_INFO field in Byte offset 0h bit 5 contains indication that the mitigation has been applied and confirmed.
| Byte Offset | Bits | Name | Description |
| 00h | 63:6 | - | Reserved. |
| 5 | ALIAS_CHECK_COMPLETE | Indicates that alias detection has completed since the last system reset and there are no aliasing addresses. Resets to 0. |
Platform Status [Attestation method for Platform]
The STRUCT_PLATFORM_STATUS Structure in Byte offset 03 bit 1 contains indication that the mitigation has been applied and confirmed.
| Byte Offset | Bits | Name | Description |
| 03h | 7:2 | - | Reserved. |
| 1 | ALIAS_CHECK_COMPLETE | Indicates that alias detection has completed since the last system reset and there are no aliasing addresses. Resets to 0. |
3rd Gen AMD EPYC™ Processors formerly codenamed “Milan" and “Milan-X”
AMD has released Platform Initialization (PI) firmware versions and SEV FW. Minimum versions of PI and SEV FW will be required to mitigate CVE-2024-21944 as indicated below.
| CVE | Mitigation | |
| CVE-2024-21944 | 5.3 (Medium) | Platform Initialization (PI) (Requires FW Flash) Milan PI 1.0.0.D (2024-07-11) + SEV FW 1.55.22 (hex 1.37.16) SPL =0x17 (2024-10-01) Please Note: Will require minimum versions PI + SEV update to mitigate CVE-2024-21944 |
| Code Name | CPUID | |
| Milan | 0x00A00F11 | |
| Milan-X | 0x00A00F12 | |
4th Gen AMD EPYC™ Processors formerly codenamed "Genoa", “Genoa-X”, “Bergamo”, and “Siena””
AMD has released Platform Initialization (PI) firmware versions and SEV FW. Minimum versions of PI and SEV FW will be required to mitigate CVE-2024-21944 as indicated below.
| CVE | Mitigation | |
| CVE-2024-21944 | 5.3 (Medium) | Platform Initialization (PI) (Requires FW Flash) Genoa PI 1.0.0.D (2024-08-20) + SEV FW 1.55.38 (hex 1.37.26) SPL =0x16 (2024-10-01) Please Note: Will require minimum versions PI + SEV update to mitigate CVE-2024-21944 |
| Code Name | CPUID | |
| Genoa | 0x00A10F11 | |
| Genoa-X | 0x00A10F12 | |
| Bergamo/Siena | 0x00AA0F02 | |
SEV TABLE
| CVE ID | SEV | SEV-ES | SEV-SNP |
| CVE-2024-21944 | N | N | Y |
Acknowledgement
AMD thanks the following for reporting this issue and engaging in coordinated vulnerability disclosure: Jesse De Meulemeester (COSIC, KU Leuven), Luca Wilke (University of Lübeck), David Oswald (University of Birmingham), Thomas Eisenbarth (University of Lübeck), Ingrid Verbauwhede (COSIC, KU Leuven), Jo Van Bulck (DistriNet, KU Leuven)
Revisions
Revision Date |
Description |
| 2024-12-10 | Initial publication |
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