Overview
CVE-2025-29934 is a medium-severity vulnerability affecting certain AMD CPUs. This bug could allow a local attacker with administrative privileges to potentially compromise the integrity of data within a Secure Encrypted Virtualization-Secure Nested Paging (SEV-SNP) guest. Specifically, the attacker might be able to run the guest using stale Translation Lookaside Buffer (TLB) entries.
Technical Details
The vulnerability stems from improper handling of TLB entries within the affected AMD CPU microcode. TLBs are caches used to speed up virtual-to-physical address translation. When a TLB entry becomes stale (outdated), it can point to an incorrect physical memory location. In the context of SEV-SNP, where guests operate in an isolated and encrypted memory space, using stale TLB entries can lead to incorrect data being accessed or modified. A local attacker with administrator privileges could potentially exploit this flaw to manipulate the execution environment of an SEV-SNP guest by influencing memory access patterns.
CVSS Analysis
The vulnerability has been assigned a CVSS score of 5.3, indicating a medium severity. This score reflects the following characteristics:
- CVSS Score: 5.3
- Attack Vector: Local (L) – Requires local access to the system.
- Attack Complexity: Low (L) – The vulnerability is relatively easy to exploit.
- Privileges Required: High (H) – Requires administrative privileges on the host system.
- User Interaction: None (N) – No user interaction is required to trigger the vulnerability.
- Scope: Changed (C) – An exploited vulnerability can affect resources beyond the attacker’s control.
- Confidentiality Impact: None (N)
- Integrity Impact: High (H) – Successful exploitation can lead to a complete loss of data integrity.
- Availability Impact: None (N)
While the attacker requires local admin access, the potential for data integrity compromise within an SEV-SNP guest makes this a noteworthy security concern.
Possible Impact
The exploitation of CVE-2025-29934 can have significant consequences, including:
- Data Corruption: Stale TLB entries can lead to the SEV-SNP guest accessing or modifying incorrect memory locations, resulting in data corruption.
- Compromised Guest Integrity: An attacker could potentially manipulate the execution of the SEV-SNP guest, compromising its overall integrity.
- Loss of Trust: The vulnerability can erode trust in the security assurances provided by SEV-SNP.
Mitigation and Patch Steps
AMD has released updated microcode to address this vulnerability. The recommended mitigation is to:
- Apply the Latest Microcode Updates: Update your AMD CPU microcode to the version specified in the AMD Security Bulletin AMD-SB-3029 (linked below). These updates typically come via BIOS/UEFI updates provided by your motherboard manufacturer or system vendor.
- Regular Security Audits: Conduct regular security audits of your systems to identify and address potential vulnerabilities promptly.
- Monitor Security Advisories: Stay informed about the latest security advisories from AMD and other relevant vendors.
It’s crucial to promptly apply the provided patches to minimize the risk of exploitation.
