CVE-2021-38093 in FFmpeg
Summary
by MITRE • 09/20/2021
Integer Overflow vulnerability in function filter_robert in libavfilter/vf_convolution.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 integer overflow vulnerability identified as CVE-2021-38093 resides within the ffmpeg media processing library, specifically in the filter_robert function located in libavfilter/vf_convolution.c. This flaw manifests in version 4.2.1 of the software and represents a critical security weakness that can be exploited by malicious actors to disrupt normal system operations. The vulnerability stems from improper handling of integer arithmetic operations within the convolution filter implementation, which is commonly used for image processing and video filtering tasks. When processing certain crafted input parameters, the function fails to properly validate or constrain integer values, leading to potential overflow conditions that can compromise system stability.
The technical implementation of this vulnerability involves the convolution filter's handling of parameters that define the size and dimensions of convolution kernels used in image processing operations. The filter_robert function processes input data to apply roberts cross edge detection algorithms, which require precise mathematical calculations involving integer values. When attackers provide maliciously crafted parameters that exceed the expected integer ranges, the arithmetic operations can produce results that wrap around to unexpected values, creating conditions where memory allocation or buffer operations may fail. This integer overflow condition can occur during the calculation of kernel dimensions or memory allocation sizes, where the overflowed values are then used in subsequent operations without proper bounds checking. The vulnerability is particularly concerning because it operates within a core filtering component that is frequently invoked during media processing workflows.
The operational impact of CVE-2021-38093 extends beyond simple denial of service conditions to potentially enable more severe consequences including arbitrary code execution or system instability. Attackers can exploit this vulnerability by crafting specially formatted media files or filter parameters that trigger the integer overflow during processing. The Denial of Service aspect occurs when the overflowed integer values cause memory allocation failures or buffer overflows that terminate the application or consume excessive system resources. However, the unspecified impacts referenced in the vulnerability description suggest that under certain conditions, this integer overflow might be exploitable for more advanced attack vectors. The vulnerability affects systems that utilize ffmpeg for processing multimedia content, including media servers, content delivery networks, and any applications that incorporate ffmpeg's filtering capabilities. Organizations using ffmpeg versions 4.2.1 and earlier are particularly at risk, as the flaw exists in widely deployed media processing software.
Mitigation strategies for CVE-2021-38093 should prioritize immediate software updates to versions that have addressed the integer overflow issue. The ffmpeg development team released patches in subsequent versions that properly validate integer inputs and prevent overflow conditions in the convolution filter implementation. System administrators should conduct comprehensive vulnerability assessments to identify all systems running affected ffmpeg versions and apply the appropriate security patches. Additionally, input validation measures should be implemented at the application level to sanitize all media file inputs before processing, particularly when dealing with untrusted content. Network segmentation and access controls can help limit exposure by restricting access to systems that process multimedia content. Organizations should also consider implementing runtime monitoring and anomaly detection systems to identify potential exploitation attempts. The vulnerability aligns with CWE-190, Integer Overflow or Wraparound, which specifically addresses issues where integer arithmetic operations produce results that exceed the range of the data type. From an ATT&CK framework perspective, this vulnerability could be categorized under T1203, Exploitation for Client Execution, when exploited in multimedia processing applications, or T1499, Endpoint Termination, when used to cause denial of service conditions. The mitigation approach should also include regular security assessments and vulnerability scanning to identify similar issues in other components of the multimedia processing pipeline.