CVE-2021-31947 in HEVC Video Extensions
Summary
by MITRE • 07/15/2021
HEVC Video Extensions Remote Code Execution Vulnerability This CVE ID is unique from CVE-2021-33775, CVE-2021-33776, CVE-2021-33777, CVE-2021-33778.
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Analysis
by VulDB Data Team • 07/17/2021
The CVE-2021-31947 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 falls under the broader category of multimedia processing security weaknesses. The flaw exists in how the system processes certain malformed HEVC video streams, creating an opportunity for attackers to execute arbitrary code with the privileges of the targeted user. The vulnerability impacts multiple Windows versions including Windows 10, Windows 11, Windows Server 2016, Windows Server 2019, and Windows Server 2022, making it particularly concerning for enterprise environments where these systems are prevalent.
The technical implementation of this vulnerability stems from insufficient input validation within the HEVC decoder component. When a specially crafted HEVC video file is processed by the affected system, the decoder fails to properly validate the structure and content of the video stream, leading to memory corruption that can be exploited to overwrite critical memory locations. This memory corruption typically manifests as buffer overflow conditions that allow attackers to inject and execute malicious code within the context of the Windows Media Foundation process. The vulnerability is particularly dangerous because it can be triggered through various attack vectors including email attachments, web downloads, or malicious websites that deliver HEVC video content. The flaw is categorized under CWE-121, which describes heap-based buffer overflow conditions, and aligns with ATT&CK technique T1203, which involves exploitation of software vulnerabilities for code execution.
The operational impact of CVE-2021-31947 extends beyond simple remote code execution, as successful exploitation can lead to complete system compromise and persistence within the target environment. Attackers can leverage this vulnerability to establish backdoors, escalate privileges, and move laterally across networks without requiring user interaction for the initial exploit. The vulnerability's remote nature means that attackers can target systems from anywhere on the internet, making it particularly attractive for advanced persistent threat actors. Organizations running affected Windows systems face significant risk of data breaches, system compromise, and potential lateral movement attacks that could affect entire network infrastructures. The vulnerability's presence in core Windows media processing components means that even legitimate video content could potentially serve as a vector for exploitation, complicating defense-in-depth strategies.
Mitigation strategies for CVE-2021-31947 should prioritize immediate patch deployment through Microsoft's regular security updates, as the vulnerability has been addressed through the July 2021 security bulletin. Organizations should also implement network-level controls to restrict access to HEVC video content from untrusted sources and consider disabling HEVC decoding capabilities where possible. Security teams should monitor for indicators of compromise related to this vulnerability, including unusual network connections, process creation patterns, and file modifications that might indicate exploitation attempts. Additionally, implementing application whitelisting policies and restricting user privileges can help limit the potential damage from successful exploitation attempts. The vulnerability serves as a reminder of the importance of maintaining up-to-date security patches and the risks associated with multimedia processing components in operating systems, particularly given the widespread use of HEVC video formats in modern digital environments.