CVE-2025-29943 Overview
CVE-2025-29943 is a hardware vulnerability affecting AMD CPUs that involves a write-what-where condition within the CPU architecture. This flaw allows an attacker with administrative privileges to modify the configuration of the CPU pipeline, potentially resulting in the corruption of the stack pointer inside an SEV-SNP (Secure Encrypted Virtualization - Secure Nested Paging) guest environment.
Critical Impact
An admin-privileged attacker can exploit this vulnerability to corrupt the stack pointer within an SEV-SNP guest, potentially undermining the security guarantees provided by AMD's hardware-based memory encryption and isolation technology.
Affected Products
- AMD CPUs with SEV-SNP support
- Systems utilizing AMD Secure Encrypted Virtualization technology
- Virtualized environments relying on SEV-SNP for guest isolation
Discovery Timeline
- 2026-01-16 - CVE CVE-2025-29943 published to NVD
- 2026-01-16 - Last updated in NVD database
Technical Details for CVE-2025-29943
Vulnerability Analysis
This vulnerability is classified under CWE-123 (Write-what-where Condition), which describes a scenario where an attacker can write an arbitrary value to an arbitrary location in memory. In the context of CVE-2025-29943, this condition exists within the AMD CPU architecture itself, specifically affecting the CPU pipeline configuration mechanisms.
The vulnerability requires local access and administrative privileges to exploit. The attack targets the integrity of SEV-SNP guest environments, which are designed to provide hardware-enforced isolation and encryption for virtual machines. SEV-SNP is intended to protect guest VMs even from a compromised hypervisor, making vulnerabilities that can bypass these protections particularly significant for cloud computing and confidential computing use cases.
Root Cause
The root cause is a write-what-where condition within AMD CPU microarchitecture that permits unauthorized modification of CPU pipeline configuration. This flaw allows privileged code to write arbitrary values to specific memory locations that control pipeline behavior, bypassing the intended isolation mechanisms of SEV-SNP.
Attack Vector
The attack requires local access to the system with administrative privileges. An attacker in this position can manipulate CPU pipeline configuration to corrupt the stack pointer within an SEV-SNP guest. This is a local attack vector that does not require user interaction.
The exploitation mechanism involves leveraging the write-what-where condition to target the CPU pipeline configuration, which can then influence the behavior of code executing within the protected SEV-SNP guest environment. While the vulnerability requires high privileges, it represents a significant concern for environments where SEV-SNP is deployed to protect sensitive workloads from potentially compromised system administrators or hypervisors.
Detection Methods for CVE-2025-29943
Indicators of Compromise
- Unexpected modifications to CPU pipeline configuration registers
- Anomalous behavior or crashes within SEV-SNP protected guest VMs
- Stack corruption errors or memory access violations in guest environments
Detection Strategies
- Monitor for privileged operations targeting CPU configuration mechanisms
- Implement hardware performance counter monitoring for anomalous CPU behavior
- Deploy integrity monitoring for SEV-SNP guest environments
Monitoring Recommendations
- Enable comprehensive logging for administrative actions on affected AMD systems
- Monitor guest VM stability and error conditions for signs of stack corruption
- Implement alerting for unusual CPU configuration changes at the hypervisor level
How to Mitigate CVE-2025-29943
Immediate Actions Required
- Review and restrict administrative access to systems utilizing SEV-SNP
- Consult AMD Security Bulletin #3027 for vendor guidance
- Assess exposure of SEV-SNP protected workloads and prioritize patching
Patch Information
AMD has published security guidance in AMD Security Bulletin #3027. Organizations should review this bulletin for specific firmware updates and mitigation instructions applicable to their AMD hardware configurations.
Workarounds
- Limit administrative access to affected systems to trusted personnel only
- Consider additional isolation layers for highly sensitive SEV-SNP workloads
- Monitor for AMD BIOS/firmware updates that address this vulnerability
- Implement defense-in-depth strategies that do not rely solely on SEV-SNP isolation
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
