CVE-2021-1643 in HEVC Video Extensions
Summary
by MITRE • 01/13/2021
HEVC Video Extensions Remote Code Execution Vulnerability This CVE ID is unique from CVE-2021-1644.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 05/04/2025
The CVE-2021-1643 vulnerability represents a critical remote code execution flaw within the HEVC Video Extensions component of Microsoft Windows operating systems. This vulnerability specifically affects the handling of H.265/HEVC video decoding processes and presents a significant security risk to enterprise environments where multimedia content processing is prevalent. The flaw exists in the way the system processes specially crafted HEVC video files, allowing attackers to execute arbitrary code with the privileges of the targeted user. This vulnerability is particularly concerning as it can be exploited through various attack vectors including email attachments, web downloads, and malicious media files that users might encounter during routine operations.
The technical implementation of this vulnerability stems from improper input validation within the HEVC video decoding library. When the system attempts to parse and decode maliciously constructed HEVC video streams, the decoder fails to properly validate buffer boundaries and memory allocations. This memory corruption issue creates an exploitable condition where attacker-controlled data can overwrite critical memory regions, potentially leading to arbitrary code execution. The vulnerability is classified under CWE-121 as a stack-based buffer overflow, which occurs when a program writes data beyond the boundaries of a fixed-length buffer allocated on the stack. The flaw is particularly dangerous because it can be triggered through legitimate video processing functions that are commonly used in multimedia applications, making detection and prevention challenging for security teams.
From an operational impact perspective, this vulnerability poses severe risks to organizations relying on Windows-based systems for multimedia processing tasks. Attackers can leverage this flaw to gain unauthorized access to systems, escalate privileges, and potentially establish persistent backdoors within network environments. The remote execution capability means that attackers do not require physical access to target systems, enabling widespread exploitation across enterprise networks. Organizations using video conferencing platforms, digital signage systems, or any application processing HEVC video content are particularly vulnerable. The vulnerability can be exploited through multiple attack surfaces including web browsers, media players, and document viewers that support HEVC format decoding, creating numerous potential entry points for threat actors. This makes the attack surface particularly broad and difficult to fully secure without comprehensive patching across all affected systems.
Mitigation strategies for CVE-2021-1643 should prioritize immediate patch deployment from Microsoft as the primary defense mechanism. Organizations must ensure that all Windows systems receive the relevant security updates promptly, as the vulnerability remains exploitable until patched. Network segmentation and monitoring should be implemented to detect unusual video processing activities that might indicate exploitation attempts. Security teams should consider disabling HEVC video decoding capabilities in applications where they are not essential for business operations. The use of exploit prevention tools and application whitelisting can provide additional layers of protection by restricting execution of untrusted code. Additionally, regular security assessments should be conducted to identify systems that may not have received the required patches, particularly in large enterprise environments where patch management can be complex. This vulnerability aligns with ATT&CK technique T1203 which involves exploitation of remote services, and T1059 which covers command and scripting interpreter usage, making it a comprehensive threat requiring multi-layered defensive approaches. Organizations should also implement network monitoring solutions capable of detecting malicious video content traffic patterns and establish incident response procedures specifically addressing remote code execution vulnerabilities in multimedia processing components.