CVE-2025-29939 is a vulnerability classified under CWE-284 (Improper Access Control) affecting AMD EPYC™ 9004 Series processors, specifically targeting the Secure Encrypted Virtualization (SEV) technology. SEV is designed to protect virtual machines by encrypting guest memory and isolating it from the hypervisor and other VMs. The vulnerability arises during the Secure Nested Paging (SNP) initialization phase, where the processor manages memory mappings for nested virtualization. An attacker with high privileges on the host system can improperly write to the Reverse Map Page (RMP), a critical data structure that tracks the mapping between guest physical addresses and host physical addresses. By manipulating the RMP, the attacker can bypass memory encryption protections, leading to potential disclosure or tampering of guest VM memory contents. This compromises both confidentiality and integrity of guest memory, undermining the security guarantees of SEV. The attack vector requires local privileged access (e.g., a compromised hypervisor or host OS) but does not require user interaction. The CVSS 4.0 base score is 6.9, reflecting a medium severity with high impact on confidentiality and integrity but limited attack vector scope. No public exploits or patches have been reported yet, indicating the need for proactive mitigation and monitoring. This vulnerability is particularly relevant for cloud providers and enterprises using AMD EPYC 9004 processors in virtualized environments relying on SEV for security.

For European organizations, the impact of CVE-2025-29939 is significant in environments utilizing AMD EPYC 9004 Series processors with SEV-enabled virtualization. Confidentiality and integrity of guest virtual machines could be compromised, risking exposure of sensitive data such as intellectual property, personal data protected under GDPR, or critical business information. This could lead to regulatory penalties, reputational damage, and operational disruptions. Cloud service providers and data centers hosting multi-tenant workloads are especially vulnerable, as a privileged attacker could potentially escape VM isolation boundaries. The requirement for high privileges limits the attack surface to insiders or attackers who have already compromised host systems, but the potential damage remains high. Given the increasing adoption of AMD EPYC processors in European data centers, the threat could affect sectors like finance, healthcare, government, and critical infrastructure. The lack of known exploits currently provides a window for mitigation before active exploitation occurs.

1. Monitor AMD and relevant vendor advisories closely for patches or microcode updates addressing this vulnerability and apply them promptly once available. 2. Restrict and harden access to host systems and hypervisors to prevent attackers from gaining the high privileges required to exploit this flaw. 3. Employ strict access controls, multi-factor authentication, and continuous monitoring on virtualization hosts. 4. Consider disabling SEV or SNP features temporarily if feasible and if risk tolerance allows, until patches are applied. 5. Use runtime security tools that can detect anomalous memory access patterns or unauthorized modifications to critical data structures like the RMP. 6. Conduct regular security audits and penetration testing focused on virtualization security controls. 7. Segment and isolate critical workloads to limit potential lateral movement in case of host compromise. 8. Collaborate with cloud providers to understand their mitigation strategies if using hosted services running on AMD EPYC 9004 processors. 9. Maintain up-to-date inventory of hardware and virtualization features in use to prioritize risk assessment and response.