CVE-2012-0850 in FFmpeg
Summary
by MITRE
The sbr_qmf_synthesis function in libavcodec/aacsbr.c in FFmpeg before 0.9.1 allows remote attackers to cause a denial of service (application crash) via a crafted mpg file that triggers memory corruption involving the v_off variable, probably a buffer underflow.
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Analysis
by VulDB Data Team • 12/12/2021
The vulnerability identified as CVE-2012-0850 resides within the FFmpeg multimedia framework, specifically in the sbr_qmf_synthesis function located in libavcodec/aacsbr.c. This flaw represents a critical security issue that affects versions of FFmpeg prior to 0.9.1, where the application becomes susceptible to remote denial of service attacks through carefully crafted media files. The vulnerability manifests when processing MPEG files that contain maliciously constructed data, leading to application instability and potential system crashes.
The technical root cause of this vulnerability stems from improper memory management within the audio synthesis processing pipeline. The sbr_qmf_synthesis function handles the synthesis of audio signals using spectral band replication techniques, which are essential for processing advanced audio codecs like AAC. During this process, the function manipulates the v_off variable, which serves as an offset pointer for memory access operations. When confronted with malformed input data, the function fails to properly validate the v_off variable bounds, resulting in memory corruption that manifests as a buffer underflow condition. This type of vulnerability falls under CWE-129, which specifically addresses improper validation of array indices, and more broadly under CWE-119, concerning weaknesses in memory management that lead to buffer overflows or underflows.
The operational impact of this vulnerability extends beyond simple application crashes, as it can be exploited by remote attackers to disrupt services through crafted media content. An attacker could potentially deliver a malicious mpg file that, when processed by an affected FFmpeg instance, would cause the application to terminate unexpectedly. This denial of service scenario could be particularly damaging in environments where FFmpeg is used as a backend processing component for media streaming services, content management systems, or any application that processes user-uploaded media files. The vulnerability's remote exploitability means that attackers do not require local access to the system, making it a significant concern for web applications and services that rely on FFmpeg for media processing.
From an attacker's perspective, this vulnerability aligns with techniques described in the MITRE ATT&CK framework under the T1499 category, specifically targeting the disruption of services through application crashes. The exploitation process requires minimal technical sophistication, as the attacker only needs to create a malformed mpg file that triggers the memory corruption. The vulnerability's presence in a widely-used multimedia processing library means that numerous applications and services could be affected, including web browsers, media players, content management systems, and streaming platforms. Organizations using affected versions of FFmpeg should prioritize immediate patching to prevent potential exploitation, as the vulnerability can be leveraged to create service disruption without requiring elevated privileges or specialized knowledge of the underlying system architecture. The fix implemented in FFmpeg 0.9.1 involved proper bounds checking for the v_off variable and enhanced input validation to prevent the memory corruption scenario that led to the buffer underflow condition.