CVE-2021-25503 in HDCP
Summary
by MITRE • 11/05/2021
Improper input validation vulnerability in HDCP prior to SMR Nov-2021 Release 1 allows attackers to arbitrary code execution.
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Analysis
by VulDB Data Team • 11/09/2021
The vulnerability identified as CVE-2021-25503 represents a critical security flaw within the High-bandwidth Digital Content Protection protocol implementation prior to the SMR November 2021 release. This issue stems from inadequate input validation mechanisms within the HDCP subsystem, which governs the protection of digital audio and video content transmitted between devices. The vulnerability specifically affects systems where HDCP is implemented for content protection, creating a potential attack vector that could be exploited by malicious actors to execute arbitrary code on affected systems.
The technical flaw manifests through insufficient validation of input parameters within the HDCP protocol handling routines. When devices process HDCP authentication requests or content transmission protocols, the system fails to properly validate the integrity and legitimacy of incoming data streams. This weakness allows attackers to craft malicious inputs that bypass normal validation checks, potentially leading to privilege escalation and unauthorized code execution. The vulnerability operates at a low-level protocol implementation stage, making it particularly dangerous as it can be exploited before the system has fully established secure communication channels.
From an operational impact perspective, this vulnerability creates significant risks for organizations relying on HDCP-protected content delivery systems. Attackers could exploit this weakness to gain unauthorized access to protected content, potentially compromising entire digital media ecosystems. The arbitrary code execution capability means that successful exploitation could lead to complete system compromise, data exfiltration, or the installation of persistent backdoors. This vulnerability affects not only consumer electronics but also enterprise systems that utilize HDCP for digital content protection, including broadcast systems, digital signage networks, and multimedia presentation environments.
Security professionals should consider this vulnerability in the context of CWE-20, which addresses "Improper Input Validation," and its relationship to ATT&CK technique T1059.007 for "Command and Scripting Interpreter: PowerShell." The exploitation pattern aligns with lateral movement and privilege escalation tactics commonly employed in advanced persistent threat campaigns. Organizations should prioritize immediate remediation through the application of the November 2021 SMR updates, while implementing network monitoring to detect potential exploitation attempts. Additional mitigations include network segmentation to limit HDCP traffic exposure, regular security assessments of digital content systems, and enhanced logging of authentication and content transmission activities. The vulnerability underscores the importance of maintaining up-to-date security patches for all digital content protection systems and demonstrates how protocol-level flaws can create systemic security risks across multiple device categories and deployment scenarios.