CVE-2025-29939: SEV Privilege Escalation Vulnerability

CVE-2025-29939 Overview

CVE-2025-29939 is an improper access control vulnerability affecting AMD's Secure Encrypted Virtualization (SEV) technology. The flaw exists in the Reverse Map Page (RMP) handling during Secure Nested Paging (SNP) initialization, which could allow a privileged attacker with local access to write to the RMP table. Successful exploitation could result in a loss of guest memory confidentiality and integrity, undermining the fundamental security guarantees that SEV-SNP is designed to provide.

Critical Impact

A privileged attacker could compromise the confidentiality and integrity of protected guest virtual machine memory by manipulating the Reverse Map Page during SNP initialization.

Affected Products

• AMD processors with Secure Encrypted Virtualization (SEV) support
• AMD SEV-SNP enabled hypervisors and virtualization platforms
• Systems utilizing AMD secure nested paging technology

Discovery Timeline

• 2026-02-10 - CVE CVE-2025-29939 published to NVD
• 2026-02-10 - Last updated in NVD database

Technical Details for CVE-2025-29939

Vulnerability Analysis

This vulnerability is classified as CWE-284 (Improper Access Control), indicating a failure in the access control mechanisms that should protect the Reverse Map Page (RMP) during the SEV-SNP initialization process. The RMP is a critical data structure in AMD's SEV-SNP architecture that tracks the ownership and security state of each page of physical memory.

During the SNP initialization phase, there exists a window where a privileged attacker with local access can exploit improper access controls to write to the RMP. This is particularly concerning because the RMP is responsible for enforcing memory isolation between the hypervisor and guest virtual machines—a core security guarantee of SEV-SNP technology.

The attack requires high privileges and local access to the target system, along with specific timing conditions during the SNP initialization process. While this limits the attack surface, the potential impact on guest VM confidentiality and integrity is significant for environments relying on SEV-SNP for workload isolation.

Root Cause

The root cause of this vulnerability lies in improper access control validation during the Secure Nested Paging initialization sequence. The RMP table, which is fundamental to maintaining memory isolation guarantees in SEV-SNP, is not adequately protected during this initialization window. This allows a privileged attacker to manipulate RMP entries before proper security constraints are fully established.

Attack Vector

The attack vector is local, requiring the attacker to have high privileges on the target system. The attacker must time their exploitation attempt during the SNP initialization phase when the improper access control condition exists. By writing malicious entries to the RMP during this window, the attacker can potentially:

1. Modify the ownership assignments of memory pages
2. Alter the security state of protected guest memory regions
3. Bypass the memory isolation guarantees provided by SEV-SNP

This attack could be leveraged by a malicious hypervisor administrator or through a separate privilege escalation vulnerability to compromise the confidentiality and integrity of guest virtual machines that should otherwise be protected from the hypervisor itself.

Detection Methods for CVE-2025-29939

Indicators of Compromise

• Unexpected modifications to RMP table entries during or after SEV-SNP initialization
• Anomalous memory access patterns targeting SEV-protected guest memory regions
• Unusual timing of SNP initialization sequences or repeated initialization attempts

Detection Strategies

• Monitor SEV-SNP initialization events and validate RMP table integrity post-initialization
• Implement firmware-level logging for RMP access operations during the initialization phase
• Deploy hypervisor integrity monitoring to detect unauthorized modifications to memory protection structures
• Audit privileged operations that occur during the SEV-SNP boot sequence

Monitoring Recommendations

• Enable AMD Platform Security Processor (PSP) logging where available to track SEV-related events
• Implement attestation verification for SEV-SNP guests to detect compromised memory isolation
• Monitor for unauthorized firmware or microcode modifications on systems with SEV capability
• Deploy SentinelOne Singularity Platform for comprehensive endpoint visibility on virtualization hosts

How to Mitigate CVE-2025-29939

Immediate Actions Required

• Review the AMD Security Bulletin #3023 for vendor-specific guidance and patches
• Apply firmware updates from AMD as they become available for affected processors
• Limit privileged access to systems running SEV-SNP protected workloads
• Audit and restrict administrative access to hypervisor management interfaces
• Consider additional isolation measures for highly sensitive SEV-SNP workloads until patches are applied

Patch Information

AMD has published Security Bulletin AMD-SB-3023 addressing this vulnerability. Organizations should consult the AMD Security Bulletin #3023 for specific patch availability, affected processor models, and updated firmware versions. Firmware updates should be applied following vendor guidelines and thorough testing in non-production environments.

Workarounds

• Restrict local privileged access to systems utilizing SEV-SNP to only essential personnel
• Implement strong authentication and authorization controls for hypervisor administration
• Consider temporarily disabling SEV-SNP for non-critical workloads if patches are not yet available and the risk is unacceptable
• Deploy additional monitoring and alerting for SEV-SNP initialization events
• Implement network segmentation to limit exposure of virtualization management interfaces

# Example: Verify SEV-SNP status and review system configuration
# Check if SEV is enabled on the system
dmesg | grep -i sev

# Review AMD-specific security features status
cat /sys/module/kvm_amd/parameters/sev
cat /sys/module/kvm_amd/parameters/sev_es
cat /sys/module/kvm_amd/parameters/sev_snp

# List running SEV-protected VMs (requires libvirt)
virsh list --all | while read line; do
  virsh dumpxml $(echo $line | awk '{print $2}') 2>/dev/null | grep -q "sev" && echo "$line - SEV enabled"
done