CVE-2009-4835 in libsndfile
Summary
by MITRE
The (1) htk_read_header, (2) alaw_init, (3) ulaw_init, (4) pcm_init, (5) float32_init, and (6) sds_read_header functions in libsndfile 1.0.20 allow context-dependent attackers to cause a denial of service (divide-by-zero error and application crash) via a crafted audio file.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 09/08/2021
The vulnerability identified as CVE-2009-4835 represents a critical denial of service weakness within the libsndfile library version 1.0.20, affecting multiple audio file parsing functions that handle various audio formats. This issue stems from insufficient input validation mechanisms within the library's core audio file processing routines, specifically impacting the htk_read_header, alaw_init, ulaw_init, pcm_init, float32_init, and sds_read_header functions. The flaw manifests when these functions encounter malformed audio files that contain invalid header parameters or corrupted data structures, leading to unexpected behavior during the audio file parsing process. The vulnerability operates under the context-dependent attack model where an attacker must provide a specifically crafted audio file to trigger the problematic code paths, making it particularly dangerous in environments where users can upload or process external audio content without proper sanitization.
The technical implementation of this vulnerability exploits a divide-by-zero error condition that occurs when the audio parsing functions attempt to compute values based on invalid or zero header fields present in the crafted audio files. When these functions encounter malformed data structures, particularly in header fields that define audio parameters such as sample rates, channel counts, or data block sizes, they perform mathematical operations that result in division by zero, causing immediate application termination. This type of error falls under CWE-369, which specifically addresses the divide by zero weakness, and represents a classic example of improper input validation leading to application instability. The functions in question are designed to initialize audio file handling contexts and read header information, but they fail to properly validate the integrity of the header data before proceeding with calculations, creating an exploitable condition that can be triggered through careful manipulation of audio file formats.
The operational impact of CVE-2009-4835 extends beyond simple service disruption, as it can be leveraged to cause complete application crashes in software systems that rely on libsndfile for audio processing capabilities. This vulnerability affects a wide range of applications including media players, audio editing software, and content management systems that process user-uploaded audio files, making it particularly dangerous in web-based environments where untrusted input is common. The vulnerability's context-dependent nature means that it requires specific conditions to be met for exploitation, but once triggered, it can cause cascading failures in applications that do not implement proper error handling or input sanitization. In security threat modeling terms, this vulnerability aligns with ATT&CK technique T1499.004, which covers network denial of service attacks, and represents a form of resource exhaustion through application crash conditions that can be amplified in systems processing multiple files or serving multiple concurrent users.
Mitigation strategies for this vulnerability require immediate patching of the libsndfile library to version 1.0.21 or later, which contains the necessary input validation fixes to prevent division by zero conditions. System administrators should also implement proper input validation and sanitization measures when processing audio files, particularly in web applications that accept user uploads. The recommended approach includes implementing comprehensive error handling that catches division by zero exceptions and gracefully handles malformed audio files without crashing the application. Additionally, applications should employ proper resource management techniques, including timeout mechanisms and memory limits, to prevent exploitation from causing extended service disruption. Security monitoring should be enhanced to detect unusual patterns of application crashes or resource consumption that may indicate exploitation attempts. Organizations using older versions of libsndfile should consider implementing network segmentation and access controls to limit exposure while patching operations are underway, as the vulnerability can be exploited remotely in applications that process external audio content without proper validation mechanisms in place.