CVE-2017-9256 in Freeware Advanced Audio Decoder
Summary
by MITRE
The mp4ff_read_stco function in common/mp4ff/mp4atom.c in Freeware Advanced Audio Decoder 2 (FAAD2) 2.7 allows remote attackers to cause a denial of service (large loop and CPU consumption) via a crafted mp4 file.
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Analysis
by VulDB Data Team • 10/21/2019
The vulnerability identified as CVE-2017-9256 affects the Freeware Advanced Audio Decoder 2 version 2.7, specifically within the mp4ff_read_stco function located in the common/mp4ff/mp4atom.c file. This issue represents a classic denial of service weakness that can be exploited by remote attackers through the careful crafting of mp4 media files. The flaw manifests when the decoder processes malformed mp4 containers that contain specially constructed stco (sample table chunk offset) atoms, leading to excessive computational overhead during parsing operations.
The technical implementation of this vulnerability stems from inadequate input validation within the mp4ff_read_stco function which fails to properly sanitize or limit the number of iterations required to process chunk offset entries in mp4 file structures. When an attacker provides a maliciously crafted mp4 file containing an excessive number of chunk offsets or malformed offset values, the function enters into a computationally intensive loop that consumes disproportionate CPU resources. This behavior aligns with CWE-772, which describes insufficient resource pool management, and specifically relates to improper loop termination conditions that allow for unbounded execution cycles.
The operational impact of this vulnerability extends beyond simple service disruption to potentially enable resource exhaustion attacks that can affect systems processing mp4 media files. Attackers can leverage this weakness to consume significant processing power and memory resources, effectively creating a denial of service condition that prevents legitimate users from accessing audio decoding services. The vulnerability is particularly concerning in environments where FAAD2 is used as a backend component for media processing, streaming services, or content delivery platforms that handle user-uploaded media files. Systems utilizing this decoder for automated media processing or real-time streaming applications would be especially vulnerable to sustained attacks that continuously consume system resources.
Mitigation strategies for CVE-2017-9256 should focus on implementing input validation and resource limiting mechanisms within the affected decoder implementation. The most effective approach involves adding bounds checking to validate the number of chunk offsets before processing and implementing maximum iteration limits to prevent excessive loop execution. Additionally, system administrators should consider deploying input sanitization layers that can detect and reject suspicious mp4 file structures before they reach the FAAD2 decoder. From an ATT&CK perspective, this vulnerability maps to T1499.004 which covers resource exhaustion attacks, and T1203 which involves exploitation of software vulnerabilities for denial of service. Organizations should also implement monitoring systems to detect unusual CPU consumption patterns that may indicate exploitation attempts, and ensure regular updates to FAAD2 implementations to address known vulnerabilities. The fix typically involves modifying the mp4ff_read_stco function to include proper validation of chunk offset counts and implementing robust error handling that prevents infinite loop conditions during media file parsing operations.