CVE-2025-20764: Critical SMI Vulnerability Allows Local Privilege Escalation

Overview

CVE-2025-20764 is a security vulnerability discovered in SMI (System Management Interface). This out-of-bounds write vulnerability could potentially allow a malicious actor who has already obtained System privilege to escalate their privileges further within the system. Exploitation requires the attacker to have System privileges already and does not require user interaction.

Technical Details

The root cause of CVE-2025-20764 lies in a missing bounds check within the SMI code. This oversight allows for a write operation to occur outside the intended memory boundaries, potentially overwriting critical system data or code. The specific vulnerable area is addressed by Patch ID ALPS10259774 and is associated with Issue ID MSV-5029.

The vulnerability allows for writing arbitrary data to memory locations accessible to SMI, enabling a malicious actor with the System privilege to potentially gain elevated privileges by manipulating kernel data structures or injecting malicious code. Because user interaction is not required, an attacker only needs the existing System privilege to take advantage of this vulnerability.

CVSS Analysis

Due to the specific characteristics of this vulnerability, the CVSS score is currently N/A. This likely reflects the reliance on pre-existing System privileges and the specific context of the SMI environment. A full CVSS score analysis requires more detailed information regarding the access vector, attack complexity, privileges required, user interaction, scope, confidentiality impact, integrity impact, and availability impact.

Possible Impact

The potential impact of CVE-2025-20764, while dependent on already having System privileges, can be significant. A successful exploit could lead to:

• Full system compromise: An attacker could gain complete control over the affected system.
• Data theft: Sensitive data could be accessed and exfiltrated.
• Malware installation: The system could be used to install and spread malware.
• Denial of service: The system could be rendered unusable.

Mitigation or Patch Steps

The recommended mitigation is to apply the official patch provided by the vendor. Specifically, ensure that Patch ID ALPS10259774 is installed on affected systems. Regularly check for and apply security updates from your device manufacturer or operating system vendor to ensure protection against this and other potential vulnerabilities.

References

MediaTek Product Security Bulletin – December 2025