CVE-2017-13251 in Android
Summary
by MITRE
In impeg2d_dec_pic_data_thread of impeg2d_dec_hdr.c, there is a possible out of bounds write due to a missing bounds check. This could lead to local escalation of privilege when running multi threaded with no additional execution privileges needed. User interaction is needed for exploitation. Product: Android. Versions: 6.0, 6.0.1, 7.0, 7.1.1, 7.1.2, 8.0, 8.1. Android ID: A-69269702.
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Analysis
by VulDB Data Team • 01/21/2020
The vulnerability identified as CVE-2017-13251 resides within the MPEG-2 decoder component of Android systems, specifically in the impeg2d_dec_pic_data_thread function located in impeg2d_dec_hdr.c. This flaw represents a critical security weakness that manifests as an out-of-bounds write condition, a common class of memory corruption vulnerability that can be exploited to gain unauthorized system access. The vulnerability affects multiple Android versions including 6.0, 6.0.1, 7.0, 7.1.1, 7.1.2, 8.0, and 8.1, indicating a widespread impact across the Android ecosystem. The issue stems from a missing bounds check within the threaded decoding process, which is particularly concerning because it operates in a multi-threaded environment where multiple processing threads handle different aspects of video decoding simultaneously.
The technical implementation of this vulnerability involves the MPEG-2 video decoder's handling of picture data within a threaded execution context. When processing video frames, the decoder fails to validate array bounds before writing data to memory locations, creating an opportunity for malicious input to overwrite adjacent memory regions. This out-of-bounds write can potentially overwrite critical program data, function pointers, or other memory structures that control program execution flow. The vulnerability is classified under CWE-787, which specifically addresses out-of-bounds write conditions, making it a well-documented and dangerous class of flaw that has been exploited in numerous security incidents. The fact that exploitation requires user interaction suggests that a malicious actor would need to convince a victim to process a specially crafted video file, but once executed, the vulnerability can lead to privilege escalation.
The operational impact of this vulnerability extends beyond simple data corruption, as it enables local privilege escalation without requiring additional execution privileges to be present initially. This means that an attacker who successfully exploits this vulnerability can elevate their privileges to the system level, potentially gaining complete control over the device. The multi-threaded nature of the decoding process makes this particularly dangerous because it allows for more complex exploitation techniques that can manipulate the execution flow of multiple threads simultaneously. The Android ID A-69269702 indicates that this vulnerability was formally recognized and tracked by Google's security team, emphasizing its severity and the need for immediate remediation. The privilege escalation capability places this vulnerability in the ATT&CK matrix under privilege escalation techniques, specifically targeting the execution of malicious code with elevated permissions.
Mitigation strategies for CVE-2017-13251 primarily involve applying the security patches released by Google as part of their regular Android security updates. The fix typically involves implementing proper bounds checking within the impeg2d_dec_pic_data_thread function to prevent the out-of-bounds write condition from occurring. Organizations and users should ensure that their Android devices are updated to the latest security patch levels, particularly those that address this specific vulnerability. Additionally, implementing application whitelisting and content filtering mechanisms can help prevent exploitation by blocking potentially malicious video files from being processed by the vulnerable decoder. The vulnerability serves as a reminder of the importance of secure coding practices, particularly around bounds checking in multi-threaded environments, and highlights the critical need for thorough code review processes to identify and remediate similar issues before they can be exploited in the wild.