CVE-2017-9254 in Freeware Advanced Audio Decoder
Summary
by MITRE
The mp4ff_read_stts 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-2017-9254 affects the Freeware Advanced Audio Decoder 2 version 2.7, specifically within the mp4ff_read_stts function located in common/mp4ff/mp4atom.c. This issue represents a classic denial of service vulnerability that exploits a flaw in the MP4 file parsing logic, allowing remote attackers to consume excessive CPU resources through carefully crafted malicious MP4 files. The vulnerability occurs when the decoder processes a specially constructed time-to-sample table within an MP4 container format, leading to an infinite or extremely long loop execution that consumes system resources and potentially renders the application unresponsive. The flaw stems from inadequate input validation and loop boundary checking within the audio decoding component, which fails to properly handle malformed MP4 metadata structures that could cause the decoder to enter an unbounded iteration cycle.
The technical implementation of this vulnerability demonstrates a failure in proper bounds checking and input sanitization within the MP4 atom parsing mechanism. When the mp4ff_read_stts function encounters a malformed time-to-sample table entry, it processes a loop that iterates based on values extracted from the malicious file without sufficient validation of the loop parameters. This creates a condition where attacker-controlled data directly influences loop iteration counts, resulting in either infinite loops or extremely long execution times that exhaust CPU cycles. The vulnerability is categorized under CWE-835, which specifically addresses the issue of loops with inadequate exit conditions, making it a clear example of improper loop control mechanisms. The affected software does not implement proper input validation to detect and reject malformed MP4 files that would cause such resource exhaustion during parsing operations.
From an operational impact perspective, this vulnerability poses significant risks to systems that utilize FAAD2 for audio decoding, particularly in environments where the decoder processes untrusted MP4 content from external sources. The denial of service condition can be triggered remotely through web-based applications, media players, or any system that employs FAAD2 as an audio processing component. Attackers can exploit this vulnerability by simply providing a maliciously crafted MP4 file that causes the decoder to enter an infinite loop, consuming 100% CPU utilization and effectively preventing legitimate audio processing operations. The attack vector is particularly concerning because it requires minimal technical expertise to execute and can be automated, making it a preferred method for disrupting services in environments that rely on FAAD2 for audio content processing. This vulnerability can be leveraged in distributed denial of service scenarios where multiple instances of the vulnerable software are targeted simultaneously, amplifying the impact of the attack.
Mitigation strategies for CVE-2017-9254 should focus on both immediate patching and defensive programming approaches. The most effective solution involves updating to a patched version of FAAD2 that includes proper bounds checking and input validation for MP4 file parsing operations. Organizations should also implement defensive measures such as input sanitization, timeout mechanisms for audio processing operations, and monitoring for unusual CPU consumption patterns that could indicate exploitation attempts. Additionally, implementing network segmentation and access controls to limit exposure to untrusted MP4 content can reduce the attack surface. The vulnerability aligns with ATT&CK technique T1499.004, which involves denial of service through resource exhaustion, and represents a common pattern in multimedia processing libraries where insufficient input validation leads to exploitable loop conditions. System administrators should also consider deploying intrusion detection systems that can identify suspicious file processing patterns and implement proper logging to track potential exploitation attempts. Regular security assessments of audio processing components and dependency updates remain critical in preventing similar vulnerabilities from being exploited in production environments.