CVE-2020-20899 in FFmpeg
Summary
by MITRE • 09/20/2021
Buffer Overflow vulnerability in function config_props in libavfilter/vf_bwdif.c in Ffmpeg 4.2.1, allows attackers to cause a Denial of Service or other unspecified impacts.
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Analysis
by VulDB Data Team • 09/29/2021
The buffer overflow vulnerability identified as CVE-2020-20899 resides within the ffmpeg media processing library, specifically in the config_props function located in the file libavfilter/vf_bwdif.c. This flaw represents a critical security weakness that affects version 4.2.1 of the ffmpeg software, which is widely deployed across various media processing applications and systems. The vulnerability stems from inadequate input validation and memory management within the backward diffusion filter implementation, creating a scenario where maliciously crafted input can trigger unexpected behavior in the underlying software infrastructure.
The technical nature of this buffer overflow occurs when the config_props function processes filter configuration parameters without proper bounds checking on input data lengths. This deficiency allows attackers to provide oversized or malformed data structures that exceed the allocated buffer space, leading to memory corruption. The vulnerability is categorized under CWE-121 as a stack-based buffer overflow, where the attacker can manipulate the program execution flow by overwriting adjacent memory locations. When the filter attempts to process malicious input, the overflow can result in program termination, arbitrary code execution, or unpredictable system behavior that compromises the stability and integrity of the media processing pipeline.
The operational impact of this vulnerability extends beyond simple denial of service scenarios, as it can potentially enable more sophisticated attacks depending on the system environment and deployment context. In media processing environments, this vulnerability could be exploited by attackers who upload malicious video files or manipulate filter parameters in streaming applications, leading to service disruption or system compromise. The affected system components include any application or service that leverages ffmpeg's backward diffusion filtering capabilities, which are commonly used in video editing software, streaming platforms, content management systems, and digital media processing workflows. The vulnerability's exploitation potential aligns with ATT&CK technique T1203, where adversaries may leverage buffer overflow conditions to gain unauthorized access or disrupt system operations.
Mitigation strategies for CVE-2020-20899 should prioritize immediate patching of affected ffmpeg installations to version 4.2.2 or later, which contains the necessary fixes for the buffer overflow condition. Organizations should also implement input validation measures at application boundaries to sanitize all media file inputs before processing, reducing the attack surface for potential exploitation attempts. Additionally, deployment of intrusion detection systems and monitoring for unusual processing patterns or memory allocation behaviors can help detect exploitation attempts. The remediation process should include thorough testing of patched environments to ensure that the fix does not introduce regressions in legitimate media processing operations while maintaining the software's core functionality and performance characteristics.