CVE-2020-21602 in libde265
Summary
by MITRE • 09/17/2021
libde265 v1.0.4 contains a heap buffer overflow in the put_weighted_bipred_16_fallback function, which can be exploited via a crafted a file.
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Analysis
by VulDB Data Team • 09/22/2021
The vulnerability CVE-2020-21602 represents a critical heap buffer overflow in libde265 version 1.0.4, specifically within the put_weighted_bipred_16_fallback function. This issue arises from insufficient bounds checking during the processing of HEVC (H.265) video files, creating a scenario where maliciously crafted input can trigger memory corruption. The vulnerability falls under the Common Weakness Enumeration category CWE-121, which deals with stack-based buffer overflow conditions, though in this case the overflow occurs in heap memory due to improper memory management during video decoding operations. The affected library serves as a crucial component in video processing pipelines, handling the decoding of HEVC encoded content that is widely used in modern multimedia applications, streaming services, and video conferencing platforms.
The technical flaw manifests when the put_weighted_bipred_16_fallback function processes weighted biprediction operations for 16-bit video samples. During this process, the function fails to properly validate the size of data buffers before performing memory writes, allowing an attacker to craft a specially formatted HEVC file that causes the program to write beyond allocated heap memory boundaries. This overflow can be triggered through normal file parsing operations when the decoder encounters specific encoding patterns in the crafted input file. The vulnerability is particularly dangerous because it operates within a video decoding context where input files are commonly processed without extensive validation, making it an attractive target for remote exploitation in applications that handle untrusted video content. The flaw demonstrates poor input validation practices and inadequate memory management that aligns with ATT&CK technique T1203, which covers exploitation of input validation vulnerabilities in multimedia processing systems.
The operational impact of this vulnerability extends across numerous applications that rely on libde265 for video decoding functionality, including media players, video streaming services, content management systems, and multimedia processing software. When exploited, the heap buffer overflow can lead to arbitrary code execution, denial of service conditions, or information disclosure, depending on the specific attack vector and system configuration. The vulnerability's exploitability is enhanced by the widespread use of HEVC encoding in modern video content, making it possible for attackers to craft malicious files that could compromise systems across various industries including entertainment, telecommunications, and cybersecurity. Organizations using affected versions of libde265 face significant risk of system compromise when processing untrusted video content, particularly in environments where automated video processing or user-uploaded content is common. The vulnerability also impacts software supply chains where libde265 is integrated as a dependency, potentially affecting multiple downstream applications and services that depend on proper video decoding capabilities. Mitigation strategies should include immediate version updates to libde265 1.0.5 or later, implementation of input validation controls, and deployment of sandboxing mechanisms for video processing operations to contain potential exploitation attempts and prevent system-wide compromise.