CVE-2018-20357 in Freeware Advanced Audio Decoder
Summary
by MITRE
A NULL pointer dereference was discovered in sbr_process_channel of libfaad/sbr_dec.c in Freeware Advanced Audio Decoder 2 (FAAD2) 2.8.8. The vulnerability causes a segmentation fault and application crash.
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Analysis
by VulDB Data Team • 06/20/2023
The vulnerability identified as CVE-2018-20357 represents a critical null pointer dereference flaw within the Freeware Advanced Audio Decoder 2 version 2.8.8 implementation. This issue specifically affects the sbr_process_channel function located in the libfaad/sbr_dec.c source file, which is responsible for processing spectral band replication data within the audio decoding pipeline. The flaw manifests when the decoder encounters malformed or specially crafted audio input data that triggers an unexpected execution path where a null pointer is dereferenced without proper validation. This type of vulnerability falls under the CWE-476 category of NULL Pointer Dereference, which is classified as a fundamental programming error that can lead to application instability and potential denial of service conditions.
The technical exploitation of this vulnerability occurs during the normal operation of the FAAD2 decoder when processing audio streams containing malformed spectral band replication information. When the sbr_process_channel function attempts to access memory through a null pointer reference, the operating system generates a segmentation fault that terminates the executing application. This behavior represents a classic denial of service vector that can be leveraged by attackers who can control the input to the decoder, potentially causing legitimate applications using FAAD2 to crash or become unresponsive. The vulnerability demonstrates poor input validation practices and inadequate error handling within the audio decoding component, which violates security best practices outlined in the CWE guidelines for preventing null pointer dereference conditions.
The operational impact of CVE-2018-20357 extends beyond simple application crashes to potentially compromise system availability and stability in environments where FAAD2 is integrated into larger multimedia frameworks or applications. Systems that rely on FAAD2 for audio processing, including media players, streaming applications, and multimedia servers, become vulnerable to denial of service attacks that can be triggered through maliciously crafted audio files. This vulnerability aligns with ATT&CK technique T1499.004 for Network Denial of Service and represents a significant concern for embedded systems and IoT devices that may incorporate FAAD2 as part of their audio processing capabilities. The flaw can be particularly problematic in server environments where audio processing is a critical function, as a single malicious audio file could cause service disruption across multiple users or applications.
Mitigation strategies for CVE-2018-20357 should focus on immediate patching of the FAAD2 library to version 2.8.9 or later, which contains the necessary fixes for the null pointer dereference issue. Organizations should implement input validation measures that sanitize audio data before processing, including implementing proper bounds checking and null pointer verification in the sbr_process_channel function. Additionally, deploying intrusion detection systems that monitor for unusual audio file processing patterns and implementing application sandboxing techniques can help reduce the attack surface. The vulnerability serves as a reminder of the importance of robust error handling in security-critical components and demonstrates the necessity of following secure coding practices as outlined in the OWASP Secure Coding Practices. System administrators should also consider implementing redundant audio processing capabilities to maintain service availability even when individual components may be vulnerable to similar issues.