CVE-2020-21597 in libde265
Summary
by MITRE • 09/17/2021
libde265 v1.0.4 contains a heap buffer overflow in the mc_chroma function, which can be exploited via a crafted a file.
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Analysis
by VulDB Data Team • 09/19/2021
The vulnerability CVE-2020-21597 represents a critical heap buffer overflow flaw within the libde265 library version 1.0.4, specifically within the mc_chroma function. This issue arises from insufficient bounds checking during the processing of HEVC (H.265) video files, creating a scenario where an attacker can craft a malicious video file that triggers memory corruption when the library attempts to decode chroma components. The flaw exists in the decoding pipeline where the library handles motion compensation operations for chroma samples, making it particularly dangerous as it can be exploited through standard media file processing workflows.
The technical exploitation of this vulnerability occurs when a crafted HEVC video file is processed by software utilizing libde265 for video decoding. The mc_chroma function fails to properly validate array indices or buffer boundaries when handling chroma motion compensation data, leading to a situation where memory writes occur beyond the allocated heap buffer space. This heap overflow creates opportunities for arbitrary code execution, memory corruption, or denial of service conditions. The vulnerability falls under CWE-121 heap-based buffer overflow, which is classified as a serious memory safety issue that can be leveraged for privilege escalation or system compromise.
From an operational perspective, this vulnerability poses significant risks to systems processing HEVC video content, including media players, streaming services, video transcoding applications, and content management systems. Attackers can exploit this through social engineering campaigns targeting users with malicious video files, or through automated scanning of web applications that process user-uploaded media. The impact extends beyond simple playback applications to include enterprise video infrastructure, content delivery networks, and any system where HEVC decoding is performed without proper input validation. The vulnerability demonstrates a classic weakness in multimedia processing libraries where input sanitization is insufficient, creating persistent security risks across multiple application domains.
Mitigation strategies for CVE-2020-21597 should prioritize immediate patching of libde265 to version 1.0.5 or later, which contains the necessary bounds checking fixes for the mc_chroma function. Organizations should implement input validation measures that sanitize all video file inputs before processing, including size limitations and format verification. Network segmentation and application whitelisting can help reduce exposure by limiting which systems can process HEVC content. Security monitoring should include detection of unusual memory allocation patterns and potential buffer overflow indicators in video processing applications. Additionally, implementing sandboxing techniques for media processing and using memory corruption detection tools can provide additional layers of defense. The vulnerability highlights the importance of regular security updates and proper input validation in multimedia libraries, as outlined in the ATT&CK framework's defense evasion and execution techniques, where buffer overflows represent common attack vectors for privilege escalation and system compromise.