CVE-2018-9841 in FFmpeg
Summary
by MITRE
The export function in libavfilter/vf_signature.c in FFmpeg through 3.4.2 allows remote attackers to cause a denial of service (out-of-array access) or possibly have unspecified other impact via a long filename.
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Analysis
by VulDB Data Team • 02/27/2023
The vulnerability identified as CVE-2018-9841 represents a critical buffer overread condition within the FFmpeg multimedia framework that affects versions through 3.4.2. This flaw exists in the export function located in libavfilter/vf_signature.c, which is part of FFmpeg's video filtering capabilities. The vulnerability manifests when processing video files with exceptionally long filenames, creating a scenario where the application attempts to access memory beyond the allocated array boundaries. This type of vulnerability falls under the category of improper input validation and memory safety issues that are commonly classified under CWE-129 and CWE-787 within the Common Weakness Enumeration framework. The issue demonstrates how seemingly benign file naming conventions can be exploited to disrupt system operations or potentially enable more severe security consequences.
The technical exploitation of this vulnerability occurs when FFmpeg processes video files containing filenames that exceed predetermined buffer limits during the signature export operation. The export function fails to properly validate the length of input filenames before attempting to store or process them, leading to an out-of-bounds memory access pattern. This memory corruption can result in unpredictable behavior including application crashes, denial of service conditions, or in some scenarios could potentially be leveraged for more sophisticated attacks if combined with other vulnerabilities. The attack vector is particularly concerning because it requires no special privileges or authentication, making it accessible to remote attackers who can simply craft malicious video files with excessively long filenames. The vulnerability aligns with ATT&CK technique T1059.007 for execution through command-line interfaces and represents a classic example of how input sanitization failures can lead to system instability.
The operational impact of CVE-2018-9841 extends beyond simple denial of service scenarios, as it affects any system or application that relies on FFmpeg for video processing or streaming operations. Media servers, content delivery networks, and video editing platforms that process user-uploaded content become particularly vulnerable, as attackers can exploit this weakness to disrupt services or potentially gain unauthorized access to system resources. The vulnerability affects not only direct FFmpeg usage but also applications that incorporate FFmpeg as a library component, creating a broad attack surface. Organizations running web applications, streaming services, or media processing pipelines must consider the implications of this vulnerability, as it could be used in distributed denial of service attacks or to compromise system availability. The memory access violation could potentially be chained with other vulnerabilities to create more severe security implications, making proper patching and mitigation strategies essential for maintaining system integrity.
Mitigation strategies for CVE-2018-9841 require immediate application of FFmpeg version 3.4.3 or later, which contains the necessary patches to address the buffer overread condition. System administrators should also implement input validation measures that limit filename lengths and sanitize all user-provided media file inputs before processing. Network-level protections such as content filtering and rate limiting can help reduce the effectiveness of potential attacks while proper monitoring and logging should be implemented to detect anomalous file processing behavior. Security teams should also consider deploying intrusion detection systems that can identify patterns consistent with exploitation attempts targeting this specific vulnerability. The fix implemented by FFmpeg developers addresses the root cause by adding proper bounds checking to the filename processing logic, ensuring that input validation occurs before memory allocation and access operations. Organizations should conduct thorough vulnerability assessments to identify all systems using vulnerable FFmpeg versions and ensure complete patch deployment across their infrastructure.