CVE-2020-21606 in libde265
Summary
by MITRE • 09/17/2021
libde265 v1.0.4 contains a heap buffer overflow fault in the put_epel_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-2020-21606 represents a critical heap buffer overflow in libde265 version 1.0.4, a widely used library for decoding h.265/HEVC video streams. This flaw exists within the put_epel_16_fallback function which handles edge pixel operations during video frame reconstruction. The vulnerability manifests when processing malformed or crafted video files that trigger improper memory access patterns during the decoding process. The heap buffer overflow occurs when the function attempts to write data beyond the allocated memory boundaries, potentially leading to arbitrary code execution or system instability.
The technical implementation of this vulnerability stems from inadequate bounds checking within the video decoding pipeline. When libde265 processes a specially crafted h.265 file, the put_epel_16_fallback function receives parameters that cause it to reference memory locations outside its allocated buffer space. This classifies the vulnerability under CWE-121, heap-based buffer overflow, and specifically aligns with CWE-787, out-of-bounds write, which is a common attack vector in multimedia processing libraries. The flaw demonstrates how video codec libraries can become attack surfaces when input validation is insufficient, particularly in functions that handle edge cases during frame reconstruction operations.
From an operational perspective, this vulnerability poses significant risks to systems processing video content, including media servers, content delivery networks, and multimedia applications. Attackers can exploit this flaw by crafting malicious video files that, when opened or processed by vulnerable applications, trigger the buffer overflow condition. The exploitation can lead to denial of service, remote code execution, or information disclosure depending on the specific system configuration and memory layout. Systems using libde265 version 1.0.4 are particularly vulnerable as this represents a known issue that was addressed in subsequent releases, making it a prime target for attackers seeking to compromise multimedia processing environments.
Mitigation strategies for CVE-2020-21606 primarily involve upgrading to libde265 version 1.0.5 or later, where the heap buffer overflow has been resolved through proper bounds checking and memory management. Organizations should conduct comprehensive vulnerability assessments to identify all systems utilizing the affected library and implement patch management procedures to ensure timely updates. Additionally, input validation measures should be implemented at application layers that process video content, including file format verification and size limitation checks. The vulnerability also highlights the importance of following ATT&CK technique T1203, "Exploitation for Client Execution," where attackers leverage library vulnerabilities to execute malicious code on target systems. Security teams should monitor for indicators of compromise related to video file processing and implement network segmentation to limit potential attack vectors. Regular security testing and fuzzing of multimedia libraries can help identify similar vulnerabilities before they can be exploited in the wild.