CVE-2013-3671 in FFmpeg
Summary
by MITRE
The format_line function in log.c in libavutil in FFmpeg before 1.2.1 uses inapplicable offset data during a certain category calculation, which allows remote attackers to cause a denial of service (invalid pointer dereference and application crash) via crafted data that triggers a log message.
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Analysis
by VulDB Data Team • 04/15/2019
The vulnerability identified as CVE-2013-3671 resides within the FFmpeg multimedia framework's libavutil library, specifically in the format_line function located in log.c. This flaw represents a classic case of improper input validation and memory management that can be exploited to execute a denial of service attack against applications utilizing FFmpeg for media processing. The vulnerability affects FFmpeg versions prior to 1.2.1, making it a significant concern for systems that rely on older versions of this widely-used multimedia processing library. The issue manifests when the format_line function processes log messages containing crafted data that triggers an invalid pointer dereference, ultimately leading to application crashes.
The technical root cause of this vulnerability stems from the improper handling of offset data within the format_line function during category calculations. When FFmpeg encounters certain malformed or crafted input data that generates log messages, the function attempts to use offset values that are inappropriate for the current processing context. This misapplication of offset data results in memory access violations where the application attempts to dereference invalid memory pointers. The flaw occurs during the log message formatting process, which is a critical component of any multimedia processing application that needs to report errors or status information. This type of vulnerability falls under CWE-476, which describes NULL pointer dereference conditions, and specifically relates to improper handling of memory offsets in buffer operations.
The operational impact of this vulnerability extends beyond simple application crashes, as it can be leveraged by remote attackers to disrupt services through carefully constructed media files or data streams. When exploited, the vulnerability can cause applications built on FFmpeg to terminate unexpectedly, potentially leading to service unavailability for legitimate users. This denial of service condition affects any application that incorporates FFmpeg's logging functionality and processes untrusted input data, including media servers, content delivery networks, and multimedia processing applications. The attack vector is particularly concerning because it requires no special privileges or authentication, making it accessible to anyone who can submit crafted data to a vulnerable system. According to ATT&CK framework, this vulnerability aligns with T1499.004, which covers network denial of service attacks, and T1059.007, covering scripting languages and command execution through input manipulation.
Mitigation strategies for CVE-2013-3671 primarily focus on updating to FFmpeg version 1.2.1 or later, which contains the necessary patches to address the improper offset handling in the format_line function. System administrators should prioritize patching affected installations, particularly in environments where FFmpeg is used to process untrusted media content. Additional protective measures include implementing input validation and sanitization for all media files processed through FFmpeg-based applications, as well as deploying network monitoring solutions to detect unusual traffic patterns that might indicate exploitation attempts. Organizations should also consider implementing application sandboxing or containerization to limit the potential impact of successful exploitation attempts. The vulnerability serves as a reminder of the importance of proper memory management and input validation in multimedia processing libraries, where malformed input can lead to critical system instability and service disruption.