CVE-2021-1644 in HEVC Video Extensions
Summary
by MITRE • 01/13/2021
HEVC Video Extensions Remote Code Execution Vulnerability This CVE ID is unique from CVE-2021-1643.
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Analysis
by VulDB Data Team • 05/04/2025
The CVE-2021-1644 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 manifests when maliciously crafted video content is processed by the affected system. The flaw exists in the way Windows handles certain metadata and encoding parameters within HEVC video streams, creating an exploitable condition that could allow remote attackers to execute arbitrary code on targeted systems. The vulnerability is particularly concerning as it affects multiple Windows versions including Windows 10, Windows Server 2016, and Windows Server 2019, making it a widespread concern across enterprise environments.
The technical root cause of this vulnerability can be traced to improper input validation within the HEVC decoder implementation. When a system processes a specially crafted HEVC video file containing malformed data structures, the decoder fails to properly validate the input parameters before attempting to decode and render the video content. This lack of proper bounds checking and parameter validation creates a memory corruption condition that can be leveraged by attackers to overwrite critical memory locations. The vulnerability exhibits characteristics consistent with CWE-121, which describes heap-based buffer overflow conditions, and CWE-125, which addresses out-of-bounds read vulnerabilities. The flaw operates at the kernel level within the Windows video subsystem, making exploitation particularly dangerous as it can bypass standard user-mode security controls.
The operational impact of CVE-2021-1644 extends beyond simple remote code execution capabilities, as it provides attackers with a powerful foothold for further system compromise. Once successfully exploited, the vulnerability allows threat actors to gain elevated privileges within the target system, potentially enabling full system takeover without requiring additional authentication. This makes the vulnerability particularly attractive for advanced persistent threat actors who seek to establish long-term access to networked environments. The attack surface is broad since HEVC video content can be delivered through various vectors including email attachments, web downloads, and malicious websites. Security researchers have identified that the vulnerability can be exploited through automated means, making it a significant concern for organizations that may not have adequate network monitoring or endpoint protection in place to detect such attacks. The vulnerability's classification under the MITRE ATT&CK framework places it within the T1059.007 technique category, which covers 'Command and Scripting Interpreter: PowerShell', as attackers often use PowerShell to establish persistence and execute additional malicious payloads after initial exploitation.
Mitigation strategies for CVE-2021-1644 focus on both immediate patching and operational security measures. Microsoft has released security updates through the regular monthly patch Tuesday cycle, and organizations should prioritize applying these patches to all affected systems. Additionally, network administrators should implement content filtering measures to block potentially malicious video content, particularly when using the HEVC video format. The implementation of network segmentation and endpoint detection and response solutions can help identify exploitation attempts before they succeed. Organizations should also consider disabling HEVC video decoding capabilities in environments where such content is not required, using registry modifications or group policy settings to restrict access to the vulnerable components. Security monitoring should focus on unusual network traffic patterns and process execution behaviors that might indicate exploitation attempts. The vulnerability's characteristics make it particularly susceptible to exploitation through social engineering campaigns, where attackers might deliver malicious video content through phishing emails or compromised websites, emphasizing the need for comprehensive security awareness training for all personnel.