CVE-2020-12355 in TXE
Summary
by MITRE • 11/12/2020
Authentication bypass by capture-replay in RPMB protocol message authentication subsystem in Intel(R) TXE versions before 4.0.30 may allow an unauthenticated user to potentially enable escalation of privilege via physical access.
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Analysis
by VulDB Data Team • 11/04/2025
The vulnerability identified as CVE-2020-12355 represents a critical authentication flaw within the Intel Trusted Execution Environment (TXE) platform's RPMB (Reliable Platform Messaging Bus) protocol message authentication subsystem. This vulnerability specifically affects Intel TXE versions prior to 4.0.30 and creates a pathway for unauthenticated attackers to potentially escalate privileges through physical access to affected systems. The RPMB protocol serves as a critical security mechanism within Intel's platform trust architecture, providing secure communication channels between the platform and trusted components. When compromised, this authentication bypass allows adversaries to manipulate protocol messages without proper verification, undermining the fundamental security assumptions of the platform's trusted execution environment.
The technical implementation of this vulnerability stems from weaknesses in how the RPMB protocol handles message authentication and replay protection mechanisms. The flaw enables a capture-replay attack vector where an attacker can intercept legitimate protocol messages and replay them at a later time to gain unauthorized access to system resources. This particular vulnerability is categorized under CWE-287 which addresses improper authentication issues, specifically focusing on authentication bypass through manipulation of authentication tokens or protocol messages. The authentication subsystem's failure to properly validate message integrity and sequence numbers creates a window of opportunity for malicious actors to exploit the trust relationships established within the platform's security framework.
The operational impact of this vulnerability extends beyond simple unauthorized access to encompass potential privilege escalation and system compromise. An attacker with physical access to a vulnerable system can leverage this flaw to bypass authentication mechanisms that are designed to protect sensitive platform operations and data. This capability represents a significant threat to the integrity of Intel's trusted execution environment, as it undermines the core principle that only authenticated and authorized entities should be able to interact with critical system components. The vulnerability's exploitation requires physical access, but this limitation does not diminish its severity given that physical access often provides attackers with additional attack surfaces and opportunities for further exploitation.
Mitigation strategies for CVE-2020-12355 primarily focus on updating affected Intel TXE firmware to version 4.0.30 or later, which includes patches addressing the authentication bypass vulnerability in the RPMB protocol message subsystem. Organizations should prioritize firmware updates across all affected platforms, particularly those hosting sensitive data or serving critical infrastructure roles. The mitigation approach aligns with ATT&CK technique T1547.001 which addresses registry run keys and startup folder, as updating firmware represents a fundamental system-level security measure that addresses the root cause of the vulnerability. Additionally, system administrators should implement physical security controls to limit access to vulnerable systems, as the attack vector requires physical presence to execute successfully. Network segmentation and monitoring solutions should be deployed to detect anomalous protocol behavior that might indicate exploitation attempts, while regular security assessments should verify that firmware updates have been properly applied and that the patched authentication mechanisms are functioning correctly.