CVE-2020-20900 in FFmpeg
Summary
by MITRE • 09/20/2021
Buffer Overflow vulnerability in function gaussian_blur in libavfilter/vf_edgedetect.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-2020-20900 resides within the ffmpeg media processing library, specifically in the gaussian_blur function located in libavfilter/vf_edgedetect.c. This flaw represents a critical security issue that affects version 4.2.1 of the ffmpeg software, which is widely deployed across various media processing applications and systems. The vulnerability manifests when the application processes certain malformed input parameters during edge detection filter operations, creating a scenario where memory boundaries are exceeded during buffer operations. The affected function handles gaussian blur computations for edge detection algorithms, making it particularly dangerous in multimedia processing environments where diverse input sources are common.
The technical exploitation of this buffer overflow occurs when an attacker provides specially crafted input parameters to the gaussian_blur function, causing the software to write data beyond the allocated memory buffer boundaries. This memory corruption vulnerability falls under the CWE-121 category of stack-based buffer overflow, where insufficient bounds checking allows attackers to overwrite adjacent memory locations. The vulnerability is particularly concerning because it can be triggered through normal media file processing operations, meaning that simply opening or processing a maliciously crafted media file could lead to system instability. The flaw demonstrates poor input validation practices and inadequate memory management within the ffmpeg filter processing pipeline, creating opportunities for attackers to manipulate the execution flow or cause system crashes.
Operationally, this vulnerability presents significant risks to organizations relying on ffmpeg for media processing tasks, including content delivery networks, video streaming services, and multimedia applications. The potential impacts extend beyond simple denial of service to include possible remote code execution scenarios, depending on the system configuration and memory layout. Attackers could leverage this vulnerability to cause system crashes, leading to service disruption and potential data loss. In enterprise environments where ffmpeg is integrated into critical workflows, such as video transcoding pipelines, this vulnerability could result in substantial operational downtime and compromise of media processing integrity. The vulnerability's exploitability is heightened by the widespread use of ffmpeg in both open source and commercial applications, making it a prime target for attackers seeking to compromise media processing infrastructure.
Mitigation strategies for CVE-2020-20900 should prioritize immediate patching of affected ffmpeg installations to version 4.3 or later, where the buffer overflow has been addressed through proper bounds checking and memory management improvements. Organizations should implement input validation measures that sanitize all parameters passed to filter functions, particularly those related to edge detection and gaussian blur operations. Network segmentation and access controls should be strengthened to limit exposure of ffmpeg processing systems to untrusted input sources. Security monitoring should include detection of unusual memory allocation patterns and potential buffer overflow attempts within media processing workflows. The vulnerability aligns with ATT&CK technique T1203 - Exploitation for Client Execution, where attackers leverage buffer overflow vulnerabilities to gain unauthorized system access or cause service disruption. System administrators should also consider implementing runtime protections such as stack canaries and address space layout randomization to mitigate potential exploitation scenarios. Regular security assessments of ffmpeg integrations and comprehensive vulnerability scanning should be conducted to identify and remediate similar issues in related software components.