CVE-2015-9138 in Android
Summary
by MITRE
In Android before 2018-04-05 or earlier security patch level on Qualcomm Snapdragon Automobile, Snapdragon Mobile, Snapdragon Wear, and Small Cell SoC FSM9055, IPQ4019, MDM9206, MDM9607, MDM9625, MDM9635M, MDM9640, MDM9645, MDM9650, MDM9655, MSM8909W, SD 210/SD 212/SD 205, SD 400, SD 410/12, SD 425, SD 430, SD 450, SD 600, SD 615/16/SD 415, SD 617, SD 625, SD 650/52, SD 800, SD 808, SD 810, SD 820, SD 820A, SD 835, SD 845, SD 850, and SDX20, when an RSA encryption operation is called, the ce_util_to_unsigned_bin is invoked to convert the input buffer to unsigned binary. The ce_util_to_unsigned_bin function, instead of operating on the size of the unsigned character buffer that is passed, operates on the address - i.e. operates on "c" instead of "*c". Decrementing the address to check if it is less than zero means that the operation will always pass, since a pointer will never be less than zero, and may result in a buffer overflow.
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Analysis
by VulDB Data Team • 01/26/2020
This vulnerability exists in Qualcomm Snapdragon SoCs used in Android devices and represents a critical buffer overflow flaw in the cryptographic processing subsystem. The issue stems from improper handling of memory boundaries during RSA encryption operations, specifically within the ce_util_to_unsigned_bin function that converts input buffers to unsigned binary format. The flaw occurs when the function incorrectly processes the address of a buffer rather than the buffer's actual size, leading to dangerous memory manipulation that can be exploited by malicious actors.
The technical root cause of this vulnerability lies in the function's improper pointer arithmetic where it compares a memory address against zero instead of the buffer size. This fundamental error in the ce_util_to_unsigned_bin function means that when an RSA operation is performed, the system fails to properly validate buffer boundaries. The comparison operates on the address value "c" rather than the dereferenced pointer "*c", which results in the condition always evaluating as true regardless of actual buffer dimensions. This allows for arbitrary memory access patterns that can overwrite adjacent memory locations, potentially leading to privilege escalation or code execution.
The operational impact of this vulnerability is severe given the widespread deployment of affected Snapdragon SoCs across various Android device categories including automotive systems, mobile phones, wearables, and small cell networks. Attackers can exploit this flaw to perform buffer overflow attacks during cryptographic operations, potentially gaining unauthorized access to sensitive system resources. The vulnerability affects multiple generations of Snapdragon processors including the SD 210, SD 400, SD 600, SD 800, and SD 850 series, making it particularly dangerous as it impacts a broad range of devices. This flaw falls under the CWE-121 category of stack-based buffer overflow, and aligns with ATT&CK techniques involving privilege escalation and code injection through memory corruption vulnerabilities.
The security implications extend beyond simple buffer overflows as this vulnerability can be leveraged to bypass cryptographic protections that are fundamental to Android security. When RSA encryption operations are performed, the improper buffer handling can lead to memory corruption that may allow attackers to execute arbitrary code with elevated privileges. This particularly affects automotive systems where such vulnerabilities could compromise vehicle security systems, and mobile devices where attackers could gain access to sensitive user data, communication channels, and system resources. The vulnerability demonstrates poor input validation practices and highlights the importance of proper memory management in cryptographic implementations. Organizations should implement immediate patching strategies and consider monitoring for potential exploitation attempts while ensuring that all affected devices receive the appropriate security updates.