CVE-2019-2106 in Android
Summary
by MITRE
In ihevcd_sao_shift_ctb of ihevcd_sao.c, there is a possible out of bounds write due to a missing bounds check. This could lead to remote code execution with no additional execution privileges needed. User interaction is 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-130023983.
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Analysis
by VulDB Data Team • 07/02/2020
The vulnerability identified as CVE-2019-2106 represents a critical out-of-bounds write flaw within the ihevcd_sao_shift_ctb function of the ihevcd_sao.c file in Android's media processing subsystem. This issue resides in the hardware-accelerated video decoding component that handles HEVC (H.265) video streams, specifically within the Sample Adaptive Offset algorithm implementation. The vulnerability manifests when processing malformed video frames that contain invalid parameters for the SAO shift operation, creating a scenario where memory writes occur beyond the allocated buffer boundaries. The flaw stems from inadequate input validation and bounds checking mechanisms that fail to properly verify the range of values used for array indexing during video frame processing operations. This vulnerability is particularly concerning as it exists within the core video decoding pipeline that processes multimedia content across various Android versions from 7.0 through 9.0, affecting a substantial portion of the Android ecosystem.
The technical exploitation of this vulnerability requires a remote attacker to craft a malicious video file containing specially formatted SAO parameters that trigger the out-of-bounds write condition. The missing bounds check occurs during the processing of Sample Adaptive Offset operations which are used to improve video quality by adjusting pixel values based on local image characteristics. When the decoder encounters invalid shift values that exceed the expected parameter ranges, the indexing calculation results in memory corruption beyond the intended buffer boundaries. This memory corruption can overwrite adjacent memory locations including function pointers, return addresses, or other critical data structures, potentially enabling arbitrary code execution. The vulnerability requires user interaction for exploitation, typically through the automatic playback of malicious media content or when the device processes video files from untrusted sources such as email attachments, web downloads, or media sharing platforms. The exploitation process leverages the standard attack patterns described in the ATT&CK framework under the T1203 technique for legitimate system processes manipulation, where the attacker abuses the normal video decoding functionality to achieve privilege escalation.
The operational impact of CVE-2019-2106 extends across multiple Android versions and device types, creating a significant security risk for users who frequently consume multimedia content from untrusted sources. The vulnerability's remote exploitation capability means that attackers can potentially compromise devices without requiring local access or elevated privileges, making it particularly dangerous in mobile environments where users regularly interact with multimedia content from unknown sources. The affected Android versions represent a large user base including devices running Android 7.0 through 9.0, covering the majority of smartphones and tablets that utilize hardware-accelerated video decoding. This vulnerability directly relates to CWE-787, which describes out-of-bounds write conditions, and aligns with the broader category of memory safety issues that have historically led to numerous remote code execution exploits in multimedia processing components. The security implications are further amplified by the fact that the vulnerability can be triggered through standard video playback operations, making it difficult for users to defend against without system-level updates or patches.
Mitigation strategies for CVE-2019-2106 primarily involve applying the security patches released by Google as part of their Android security bulletins, which include fixes for the bounds checking implementation in the video decoding component. Device manufacturers should prioritize the deployment of these updates across affected Android versions, particularly for devices running Android 7.0 through 9.0 where the vulnerability is present. Users should ensure their devices receive timely security updates and avoid downloading multimedia content from untrusted sources. Additional protective measures include implementing network-level filtering to block suspicious media content, enabling automatic security updates, and maintaining awareness of the potential risks associated with processing media files from unknown origins. The vulnerability also highlights the importance of input validation and bounds checking in multimedia processing components, as recommended by security best practices and industry standards such as those outlined in the OWASP Top 10 and NIST guidelines for secure coding practices. Organizations should also consider implementing sandboxing mechanisms and privilege separation techniques to limit the potential impact of similar vulnerabilities in their systems, aligning with the defense-in-depth principles described in the MITRE ATT&CK framework.