CVE-2019-2128 in Android
Summary
by MITRE
In ACELP_4t64_fx of c4t64fx.c, there is a possible out of bounds write due to a missing bounds check. This could lead to local escalation of privilege with no additional execution privileges needed. User interaction is not needed for exploitation. Product: Android. Versions: Android-7.0 Android-7.1.1 Android-7.1.2 Android-8.0 Android-8.1 Android-9. Android ID: A-132647222.
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Analysis
by VulDB Data Team • 08/01/2020
The vulnerability identified as CVE-2019-2128 represents a critical out-of-bounds write flaw within the ACELP_4t64_fx function of the c4t64fx.c file in Android's audio processing subsystem. This issue resides in the Adaptive Multi-Rate (AMR) codec implementation that handles speech encoding and decoding operations. The flaw manifests when processing audio data through the ACELP (Algebraic Code Excited Linear Prediction) algorithm, specifically during the 4t64 frame processing routine. The missing bounds check allows maliciously crafted audio data to write beyond the allocated memory buffer, potentially corrupting adjacent memory regions and compromising system stability. This vulnerability is particularly concerning as it affects multiple Android versions including 7.0 through 9.0, representing a significant portion of the Android ecosystem that was vulnerable to exploitation.
The technical implementation of this vulnerability stems from inadequate input validation within the ACELP_4t64_fx function where array indexing operations lack proper boundary verification. When the system processes audio frames containing malformed data, the code fails to validate whether the calculated array indices remain within the allocated buffer boundaries. This type of flaw falls under CWE-129, which specifically addresses insufficient bounds checking in array access operations. The vulnerability creates a scenario where an attacker can manipulate the input data to cause memory corruption that may result in arbitrary code execution. The exploitation requires no user interaction, making it particularly dangerous as it can be triggered through automated means during normal audio processing operations.
The operational impact of this vulnerability extends beyond simple memory corruption, as it enables local privilege escalation without requiring additional execution privileges or user interaction. This means that any application or process running with standard user privileges could potentially leverage this flaw to gain elevated system permissions. The vulnerability's exploitation pathway follows ATT&CK technique T1068, which involves exploiting legitimate credentials and privileges to elevate access rights. The Android operating system's audio processing framework becomes a potential attack vector where malicious audio files could trigger the out-of-bounds write condition. This creates a significant security risk as audio processing occurs frequently during normal device operation, providing multiple opportunities for exploitation.
Mitigation strategies for CVE-2019-2128 should prioritize immediate patch deployment from Google, which addressed this vulnerability in Android security updates released in 2019. System administrators should ensure all affected Android devices receive the latest security patches, particularly focusing on the media framework components that handle audio processing. Additionally, implementing runtime monitoring and input validation controls can help detect anomalous audio processing patterns that might indicate exploitation attempts. The fix typically involves adding proper bounds checking to array access operations within the ACELP_4t64_fx function, ensuring that all calculated indices remain within valid buffer boundaries. Organizations should also consider implementing application sandboxing and privilege separation techniques to limit the potential impact of any successful exploitation attempts. Regular security audits of audio processing libraries and codecs should be conducted to identify similar vulnerabilities in other system components.