CVE-2017-9221 in Freeware Advanced Audio Decoder
Summary
by MITRE
The mp4ff_read_mdhd function in common/mp4ff/mp4atom.c in Freeware Advanced Audio Decoder 2 (FAAD2) 2.7 allows remote attackers to cause a denial of service (invalid memory read and application crash) via a crafted mp4 file.
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Analysis
by VulDB Data Team • 10/20/2019
The CVE-2017-9221 vulnerability resides within the Freeware Advanced Audio Decoder 2 (FAAD2) version 2.7, specifically in the mp4ff_read_mdhd function located in the common/mp4ff/mp4atom.c file. This flaw represents a classic buffer over-read condition that can be exploited by remote attackers through the careful crafting of malicious mp4 media files. The vulnerability demonstrates how improper input validation in multimedia decoding libraries can lead to system instability and denial of service conditions that affect applications relying on FAAD2 for audio processing. The affected component processes metadata headers within mp4 containers, specifically the media header atom (mdhd) which contains timing and duration information essential for proper media playback.
The technical exploitation of this vulnerability occurs when the mp4ff_read_mdhd function attempts to read memory locations that are either uninitialized or outside the bounds of allocated memory structures. This invalid memory read typically results in a segmentation fault or access violation that causes the application to crash abruptly. The flaw stems from inadequate bounds checking during the parsing of mp4 file structures, where the decoder fails to properly validate the length and content of the media header atom before attempting to access its constituent fields. This type of vulnerability aligns with CWE-129, which describes improper validation of length fields, and CWE-125, which covers out-of-bounds read conditions. The vulnerability operates at the application layer within the multimedia processing stack, making it particularly dangerous as it can be triggered through normal media file processing operations without requiring special privileges or complex attack vectors.
The operational impact of CVE-2017-9221 extends beyond simple application crashes to potentially disrupt broader media processing workflows and services that depend on FAAD2 for audio decoding. Systems utilizing FAAD2 as part of their audio processing pipeline, including media servers, streaming applications, and content management systems, could experience service degradation or complete outages when processing maliciously crafted mp4 files. The vulnerability affects any software that incorporates FAAD2 as a library component for handling mp4 audio streams, creating a wide attack surface across various applications and platforms. This type of denial of service condition can be particularly problematic in enterprise environments where media processing systems must maintain high availability and reliability. The vulnerability's remote exploitation capability means that attackers can trigger the condition from external networks without requiring physical access to target systems, making it a significant concern for networked applications and services.
Mitigation strategies for CVE-2017-9221 should focus on both immediate patching and defensive programming approaches. The primary remediation involves updating to FAAD2 version 2.8 or later, where the vulnerability has been addressed through proper bounds checking and input validation mechanisms. Organizations should implement comprehensive patch management processes to ensure all systems utilizing FAAD2 are updated promptly. Additionally, defensive measures such as input sanitization, file format validation, and implementing robust error handling can provide additional layers of protection. The vulnerability demonstrates the importance of adhering to secure coding practices as outlined in the ATT&CK framework under the T1059.007 technique for command and scripting interpreter, where proper input validation prevents exploitation of memory corruption vulnerabilities. Network segmentation and file filtering mechanisms can also help reduce the attack surface by preventing unauthorized access to systems that process mp4 media files. Security monitoring should include detection of unusual application crash patterns and memory access violations that may indicate exploitation attempts.