CVE-2024-36347 in EPYC
Summary
by MITRE • 06/28/2025
Improper signature verification in AMD CPU ROM microcode patch loader may allow an attacker with local administrator privilege to load malicious microcode, potentially resulting in loss of integrity of x86 instruction execution, loss of confidentiality and integrity of data in x86 CPU privileged context and compromise of SMM execution environment.
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Analysis
by VulDB Data Team • 07/01/2025
The vulnerability identified as CVE-2024-36347 represents a critical flaw in AMD CPU ROM microcode patch loader mechanisms that undermines fundamental security assurances within x86 processor architectures. This weakness resides in the improper signature verification process that governs how microcode updates are validated and loaded into CPU cores, creating a pathway for malicious actors to bypass security controls designed to protect the most privileged execution environments. The vulnerability specifically targets the microcode patch loading infrastructure that operates below the operating system level, making it particularly dangerous as it can affect the core instruction execution integrity of processors. The flaw enables attackers with local administrative privileges to craft and inject malicious microcode patches that will be accepted and executed by the processor without proper validation, effectively subverting the security model that protects against unauthorized code execution at the hardware level.
The technical nature of this vulnerability stems from inadequate cryptographic verification mechanisms within the microcode patch loading process, which falls under CWE-327 - Use of a Broken or Risky Cryptographic Algorithm and CWE-347 - Improper Verification of Cryptographic Signature. The microcode loader's failure to properly verify digital signatures allows for the execution of unauthenticated code within the CPU's most privileged execution context, where the processor operates with the highest level of access rights and can manipulate all system resources. This weakness creates an attack surface that extends beyond traditional software security boundaries into the realm of hardware-based security controls, where microcode updates should be treated as critical system components requiring rigorous validation. The improper signature verification mechanism essentially removes the cryptographic guarantee that ensures only legitimate, authorized microcode updates can be loaded, leaving the processor vulnerable to malicious modifications that could persist across system reboots and remain undetected by conventional security monitoring tools.
The operational impact of CVE-2024-36347 extends far beyond typical software vulnerabilities as it compromises fundamental security assurances at the processor level, affecting the integrity of x86 instruction execution and potentially enabling complete system compromise. Attackers who exploit this vulnerability can manipulate the processor's behavior to execute arbitrary code in privileged contexts, potentially gaining access to confidential data stored within the CPU's protected memory spaces and compromising the security of the System Management Mode (SMM) execution environment. The SMM is a critical component that operates outside the normal operating system execution context and handles sensitive system functions such as power management, hardware initialization, and security features. When compromised, SMM execution environments can provide attackers with persistent access to system resources and the ability to manipulate system behavior at the most fundamental level, making this vulnerability particularly dangerous for enterprise environments and systems requiring high security assurances. The impact includes potential data leakage, system compromise, and the ability to maintain persistent access that could survive operating system reinstallation or other standard security measures.
Mitigation strategies for CVE-2024-36347 require a multi-layered approach that addresses both immediate protection and long-term security improvements in processor-based security architectures. System administrators should prioritize applying firmware updates from AMD that address the signature verification flaw, although the effectiveness of such updates may be limited by the nature of the vulnerability existing within the microcode loading infrastructure itself. Organizations should implement monitoring solutions capable of detecting anomalous microcode loading behaviors and establish strict access controls to prevent unauthorized local administrator access that could enable exploitation. The vulnerability's classification under ATT&CK technique T1543.003 - Create or Modify System Process: Windows Service and T1068 - Exploitation for Privilege Escalation highlights the need for enhanced privilege management and access control measures. Additionally, security teams should consider implementing hardware security modules and trusted platform modules that can provide additional cryptographic verification layers beyond what is offered by the vulnerable microcode loader. Given the nature of the vulnerability, organizations should also prepare for potential long-term remediation strategies that may require processor-level security enhancements or alternative hardware configurations that can provide stronger guarantees against unauthorized microcode modifications. The vulnerability underscores the critical importance of maintaining robust hardware security controls and the need for continuous monitoring of processor-level security mechanisms that operate outside traditional software security boundaries.