CVE-2019-2156 in Android
Summary
by MITRE
In libxaac, there is a possible out of bounds read due to a missing bounds check. This could lead to information disclosure with no additional execution privileges needed. User interaction is needed for exploitation. Product: AndroidVersions: Android-10Android ID: A-112552816
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 09/11/2020
The vulnerability identified as CVE-2019-2156 resides within the libxaac library component of Android systems, specifically affecting Android 10 installations. This issue represents a classic out-of-bounds read condition that occurs when the system fails to properly validate array indices or buffer boundaries during audio processing operations. The flaw manifests in the Advanced Audio Coding (AAC) decoding functionality where the library processes audio data without adequate bounds checking mechanisms. This particular vulnerability falls under the CWE-129 category of Improper Input Validation, specifically addressing issues related to insufficient boundary checks in array access operations. The vulnerability is classified as a remote code execution risk but requires user interaction to exploit, making it a medium severity threat that can potentially lead to information disclosure.
The technical implementation of this vulnerability stems from how libxaac handles malformed audio data during the decoding process. When processing audio streams, the library does not validate the size or structure of incoming data before attempting to read from memory locations. This allows an attacker to craft specially formatted audio files that, when played or processed by the affected Android system, trigger the out-of-bounds memory access. The missing bounds check typically occurs during the parsing of AAC frame headers or when processing specific audio codec parameters. The system's failure to validate these inputs creates a scenario where memory reads occur beyond the allocated buffer boundaries, potentially exposing sensitive data from adjacent memory regions. This type of vulnerability aligns with ATT&CK technique T1059.007 for Command and Scripting Interpreter: JavaScript and T1566.001 for Phishing: Spearphishing Attachment, as it can be exploited through malicious audio files delivered via email or other attack vectors.
The operational impact of CVE-2019-2156 extends beyond simple information disclosure, as the out-of-bounds read could potentially expose system memory contents including cryptographic keys, user credentials, or other sensitive information stored in adjacent memory locations. While the vulnerability does not require additional execution privileges, it does necessitate user interaction, meaning that a malicious actor would need to convince a target to play or process a specially crafted audio file. The exploitation typically occurs when a user opens or plays an audio file that has been manipulated to contain malicious data structures. This attack vector represents a significant concern for enterprise environments where users may encounter untrusted audio content through various channels including email attachments, web downloads, or social media platforms. The vulnerability affects the Android Media Framework and specifically impacts the AudioFlinger service, which is responsible for audio processing and playback operations.
Mitigation strategies for CVE-2019-2156 should focus on both immediate patching and operational security measures. Android users and administrators should apply the security patches released by Google as part of the Android Security Bulletin for the affected Android 10 version. The patch addresses the missing bounds check by implementing proper input validation before memory access operations. Organizations should also implement network-level controls to filter audio content and prevent the automatic playback of potentially malicious files. Security monitoring should include detection of unusual audio processing activities or memory access patterns that might indicate exploitation attempts. Additional protective measures include user education about the risks of opening untrusted audio files, implementing application whitelisting for audio processing applications, and configuring mobile device management policies to restrict audio content downloads from unknown sources. The vulnerability demonstrates the importance of proper input validation in multimedia processing libraries and highlights the need for comprehensive security testing of audio codec implementations. This issue also underscores the necessity of following secure coding practices as outlined in the OWASP Secure Coding Guidelines and the CERT Secure Coding Standards, particularly in areas related to memory management and input validation.