CVE-2017-15853 in Android
Summary
by MITRE
In Qualcomm Android for MSM, Firefox OS for MSM, and QRD Android with all Android releases from CAF using the Linux kernel before security patch level 2018-04-05, while processing PTT commands, ptt_sock_send_msg_to_app() is invoked without validating the packet length. If the packet length is invalid, then a buffer over-read can occur.
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Analysis
by VulDB Data Team • 02/08/2021
The vulnerability identified as CVE-2017-15853 represents a critical buffer over-read flaw within Qualcomm's Android and Firefox OS implementations that affect multiple device platforms through the Linux kernel. This weakness exists in systems utilizing the Linux kernel before the security patch level of 2018-04-05, impacting all Android releases from the Code Aurora Forum. The vulnerability specifically manifests during the processing of PTT (Push-to-Talk) commands, which are commonly used in enterprise and public safety communication systems where immediate voice communication is essential for emergency response and coordination.
The technical root cause of this vulnerability lies in the function ptt_sock_send_msg_to_app() which fails to properly validate packet length parameters before processing incoming PTT messages. When malformed or excessively large packets are received, the function attempts to read beyond the allocated buffer boundaries, creating a condition where arbitrary memory locations can be accessed and potentially read. This buffer over-read scenario occurs because the system does not perform adequate input validation on the packet length field, allowing attackers to craft malicious PTT commands that trigger the vulnerable code path. The flaw falls under the CWE-125 vulnerability category, which specifically addresses out-of-bounds read conditions in software implementations. The attack surface is particularly concerning given that PTT functionality is often implemented in communication-critical applications where system stability and security are paramount.
The operational impact of this vulnerability extends beyond simple memory corruption, as it could potentially enable attackers to extract sensitive information from kernel memory spaces, including cryptographic keys, user credentials, or system configuration data. The vulnerability is particularly dangerous in enterprise environments where PTT systems are deployed for mission-critical communications, as it could allow unauthorized parties to gain insights into communication patterns, system internals, or potentially escalate privileges within the affected devices. Attackers could leverage this vulnerability to perform reconnaissance activities or to gather intelligence about the targeted system's memory layout, which could subsequently be used to exploit additional vulnerabilities or to develop more sophisticated attack vectors.
Mitigation strategies for this vulnerability require immediate deployment of security patches from Qualcomm and device manufacturers, specifically targeting the Linux kernel versions before the 2018-04-05 patch level. Organizations should implement network segmentation and monitoring to detect unusual PTT command traffic patterns that might indicate exploitation attempts. The vulnerability demonstrates the importance of input validation in kernel-level code and aligns with ATT&CK technique T1068 which covers local privilege escalation through kernel exploits. Device administrators should also consider implementing firmware update policies that ensure all connected devices receive timely security patches, particularly those that handle real-time communication protocols like PTT. The vulnerability serves as a reminder of the critical need for robust buffer management and validation in embedded systems, especially in mobile platforms where communication protocols are integral to system functionality and security.