CVE-2017-9993 in FFmpeg
Summary
by MITRE
FFmpeg before 2.8.12, 3.0.x and 3.1.x before 3.1.9, 3.2.x before 3.2.6, and 3.3.x before 3.3.2 does not properly restrict HTTP Live Streaming filename extensions and demuxer names, which allows attackers to read arbitrary files via crafted playlist data.
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Analysis
by VulDB Data Team • 12/09/2022
The vulnerability identified as CVE-2017-9993 represents a critical file inclusion flaw within the FFmpeg multimedia framework that affects multiple versions across several release branches. This vulnerability resides in the HTTP Live Streaming (HLS) handling capabilities of FFmpeg, specifically in how the software processes playlist data and validates filename extensions and demuxer names. The flaw allows malicious actors to manipulate the playback process by crafting specially designed playlist files that can trick FFmpeg into accessing arbitrary files on the system where the software is running. This issue stems from insufficient input validation and improper restriction of filename extensions, creating a path for unauthorized file access that could potentially expose sensitive system information.
The technical exploitation of this vulnerability occurs through the manipulation of HLS playlist files that contain crafted filename extensions or demuxer names. When FFmpeg processes these malicious playlists, it fails to properly validate the extensions or demuxer specifications, allowing attackers to specify arbitrary file paths that should normally be restricted. The vulnerability is particularly dangerous because it operates at the demuxer level where FFmpeg interprets and processes multimedia streams, enabling attackers to potentially read files from the local filesystem that they would not normally have access to. This flaw is categorized under CWE-22 which specifically addresses improper limitation of a pathname to a restricted directory, commonly known as path traversal attacks. The vulnerability exists in the core file handling logic where the software should enforce strict validation but instead permits the use of relative or absolute paths that can traverse the filesystem.
From an operational perspective, this vulnerability poses significant risks to systems that utilize FFmpeg for processing multimedia content, particularly in server environments or applications that accept user-uploaded playlist files. Attackers could exploit this weakness to access sensitive files such as configuration files, system credentials, or other confidential data stored on the same server. The impact extends beyond simple information disclosure, as the vulnerability could potentially enable further exploitation if sensitive files contain executable code or if the attacker can leverage the access to perform additional malicious activities. The vulnerability is particularly concerning in web applications that use FFmpeg for video processing, as it could allow remote attackers to access server files without authentication, making it a serious concern for cloud services, content management systems, and multimedia processing platforms. This vulnerability aligns with ATT&CK technique T1059 which covers command and scripting interpreter usage, and T1083 which addresses file and directory discovery, as attackers could use the vulnerability to enumerate and access system files.
The recommended mitigation strategy involves upgrading to patched versions of FFmpeg where the vulnerability has been addressed. Users should immediately update to FFmpeg version 2.8.12, 3.1.9, 3.2.6, or 3.3.2, depending on their current version, as these releases contain the necessary fixes to properly validate filename extensions and demuxer names in HLS playlist processing. Additionally, administrators should implement strict input validation for any user-provided playlist files and consider implementing network segmentation to limit access to FFmpeg processing capabilities. Organizations should also monitor their systems for any unauthorized file access attempts and implement proper logging and alerting mechanisms to detect potential exploitation attempts. The vulnerability demonstrates the importance of proper input validation and access control mechanisms in multimedia processing frameworks, highlighting how seemingly benign file handling operations can become security risks when proper validation is not implemented.