CVE-2007-6278 in libFLAC
Summary
by MITRE
Free Lossless Audio Codec (FLAC) libFLAC before 1.2.1 allows user-assisted remote attackers to force a client to download arbitrary files via the MIME-Type URL flag (-->) for the FLAC image file in a crafted .FLAC file.
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Analysis
by VulDB Data Team • 01/12/2025
The vulnerability identified as CVE-2007-6278 affects the Free Lossless Audio Codec implementation within libFLAC versions prior to 1.2.1, representing a significant security flaw in multimedia processing software. This issue manifests through a specific manipulation of the FLAC image file format that enables malicious actors to exploit client-side applications during media file handling. The vulnerability operates through a user-assisted remote attack vector, meaning that successful exploitation requires some form of user interaction or engagement with a crafted malicious file. The technical mechanism involves the manipulation of MIME-Type URL flags, specifically the "-->" sequence, within the image data portion of FLAC files, which can cause affected clients to initiate unauthorized network requests.
The core technical flaw resides in the insufficient validation and sanitization of image data within FLAC files, particularly when processing embedded image metadata. When libFLAC processes a crafted FLAC file containing malicious image data with the specific MIME-Type URL flag pattern, the library fails to properly validate the content and instead interprets the crafted URL reference as an actual network request directive. This misinterpretation occurs during the parsing of image data sections within the FLAC container format, where the library's handling of URL references lacks proper bounds checking and content validation mechanisms. The vulnerability specifically targets the image processing components of the FLAC library, which are responsible for embedding and displaying album art or other visual metadata within audio files, making it particularly dangerous in environments where users frequently process multimedia content from untrusted sources.
The operational impact of this vulnerability extends beyond simple file download capabilities, creating potential pathways for more sophisticated attacks within affected systems. When a user opens a maliciously crafted FLAC file with an affected version of libFLAC, the client application may automatically attempt to download additional content from remote servers specified in the manipulated image data, potentially leading to unauthorized data exfiltration, malware delivery, or network reconnaissance activities. This vulnerability particularly affects media players, audio processing applications, and any software that utilizes libFLAC for audio file handling, creating widespread exposure across various client-side applications. The user-assisted nature of the attack means that successful exploitation requires some form of user interaction, such as opening the malicious file, but once triggered, the vulnerability can execute automated network requests without further user intervention, making it particularly insidious in targeted attack scenarios.
The vulnerability aligns with CWE-20, which describes improper input validation, specifically in the context of how the FLAC library processes image metadata without adequate sanitization of URL references. From an ATT&CK framework perspective, this vulnerability maps to techniques involving social engineering through media files and command and control communications through file-based attacks. The attack chain typically involves crafting a malicious FLAC file with embedded image data containing crafted URL references, distributing this file through various vectors such as email attachments, file sharing platforms, or compromised websites, and waiting for users to open the file with vulnerable software. The remediation strategy focuses on updating to libFLAC version 1.2.1 or later, which includes proper input validation and URL sanitization mechanisms. Organizations should implement comprehensive software update policies, particularly for multimedia processing libraries, and consider network monitoring to detect unauthorized file download activities that may result from exploitation of this vulnerability. Additionally, user education regarding the risks of opening untrusted multimedia files and implementing sandboxing techniques for media file processing can significantly reduce the attack surface and mitigate potential impacts of this vulnerability.