CVE-2021-38089 in FFmpeg
Summary
by MITRE • 09/20/2021
Buffer Overflow vulnerability in function config_input in libavfilter/vf_bm3d.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-2021-38089 resides within the libavfilter component of FFmpeg version 4.2.1, specifically within the config_input function located in the vf_bm3d.c file. This vulnerability represents a critical security flaw that can be exploited by malicious actors to disrupt system operations and potentially execute arbitrary code. The flaw occurs when the application processes video filter configurations, particularly those involving the bm3d temporal denoising filter, which is commonly used for video processing and enhancement tasks.
The technical implementation of this buffer overflow stems from inadequate input validation and bounds checking within the config_input function. When FFmpeg processes video streams that utilize the bm3d filter, the application fails to properly validate the size of input parameters before copying them into fixed-size buffers. This allows an attacker to provide maliciously crafted input data that exceeds the allocated buffer space, resulting in memory corruption. The vulnerability is classified as a classic stack-based buffer overflow according to CWE-121, which occurs when data is copied into a buffer without proper size validation, leading to overwriting adjacent memory locations. The flaw demonstrates characteristics of CWE-787, which specifically addresses out-of-bounds writes that can occur when an application writes data past the end of a buffer.
The operational impact of this vulnerability extends beyond simple denial of service conditions, as it can potentially enable more severe security consequences. An attacker who successfully exploits this vulnerability could cause FFmpeg processes to crash, leading to service disruption and potential denial of service for legitimate users. However, the more concerning aspect is the potential for remote code execution, which would allow attackers to gain unauthorized control over systems running vulnerable versions of FFmpeg. This is particularly dangerous in environments where FFmpeg is used as part of content management systems, media processing pipelines, or web applications that handle user-uploaded video content. The vulnerability affects systems where FFmpeg is integrated into larger software ecosystems, making it a significant concern for organizations relying on video processing capabilities.
Mitigation strategies for CVE-2021-38089 should prioritize immediate patching of affected FFmpeg installations to version 4.4 or later, where the buffer overflow has been addressed through proper input validation and bounds checking mechanisms. Organizations should also implement network segmentation and access controls to limit exposure of FFmpeg components to untrusted inputs, particularly in web-facing applications. Input sanitization measures should be implemented at application layers that interface with FFmpeg to validate and sanitize all video processing parameters before they reach the vulnerable code paths. Security monitoring should include detection of abnormal resource consumption patterns that might indicate exploitation attempts. Additionally, organizations should consider implementing sandboxing techniques and privilege separation to limit the potential impact of successful exploitation, as outlined in ATT&CK technique T1059.007 for command and scripting interpreter usage. The vulnerability also highlights the importance of regular security assessments and dependency updates to prevent similar issues from arising in other components of multimedia processing stacks.