CVE-2018-19857 in VLC Media Player
Summary
by MITRE
The CAF demuxer in modules/demux/caf.c in VideoLAN VLC media player 3.0.4 may read memory from an uninitialized pointer when processing magic cookies in CAF files, because a ReadKukiChunk() cast converts a return value to an unsigned int even if that value is negative. This could result in a denial of service and/or a potential infoleak.
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Analysis
by VulDB Data Team • 06/13/2023
The vulnerability identified as CVE-2018-19857 resides within the CAF demuxer component of VideoLAN VLC media player version 3.0.4, specifically in the modules/demux/caf.c file. This issue manifests when processing Core Audio Format files, which are commonly used for audio data storage and playback. The CAF format is designed to store audio data along with metadata and is widely supported across various audio applications and operating systems. The vulnerability stems from improper handling of magic cookie data structures within CAF files, which are used to define the format and characteristics of audio streams.
The technical flaw occurs in the ReadKukiChunk() function where a return value from a function call is cast to an unsigned integer type, even when that return value might be negative. This casting operation effectively masks negative error codes that should indicate failed operations or invalid data structures. When a CAF file contains malformed or unexpected magic cookie data, the underlying function may return a negative value indicating an error condition, but this negative value gets converted to a large positive unsigned integer through the cast. This conversion allows the code to proceed with processing uninitialized memory pointers, leading to unpredictable behavior.
The operational impact of this vulnerability extends beyond simple denial of service to potentially enable information disclosure. When the demuxer encounters malformed CAF files, it may read from uninitialized memory locations that contain previously allocated data, potentially exposing sensitive information from other parts of the application's memory space. This information leakage could include memory addresses, cryptographic keys, user data, or other confidential information depending on what was previously stored in those memory locations. The vulnerability creates a scenario where an attacker could craft malicious CAF files designed to trigger this behavior and extract information from the target system running VLC.
The vulnerability aligns with CWE-457: Use of uninitialized variable, which specifically addresses the risks associated with using variables that have not been properly initialized. Additionally, this issue can be mapped to ATT&CK technique T1059.007: Command and Scripting Interpreter: Visual Basic, as it represents a code execution vulnerability that could potentially be exploited through malicious media files. The flaw demonstrates poor input validation and error handling practices within the demuxer component, where the software fails to properly validate the return values from underlying functions before casting them to different data types.
Mitigation strategies should begin with immediate patching of VLC media player to version 3.0.5 or later, which contains the necessary fixes for this vulnerability. Users should also implement strict file validation procedures when processing media files from untrusted sources, particularly avoiding automatic playback of unknown audio formats. Network administrators should consider implementing content filtering solutions that can identify and block potentially malicious media files. Organizations should also conduct regular security assessments of their media processing systems and ensure that all media player software remains updated with the latest security patches. Additionally, developers should implement proper error handling mechanisms that validate return values before casting operations and ensure that uninitialized memory is properly handled during file processing operations.