CVE-2016-2502 in Android
Summary
by MITRE
drivers/usb/gadget/f_serial.c in the Qualcomm USB driver in Android before 2016-07-05 on Nexus 5X and 6P devices allows attackers to gain privileges via a large size in a GSER_IOCTL ioctl call, aka Android internal bug 27657963 and Qualcomm internal bug CR997044.
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Analysis
by VulDB Data Team • 09/01/2022
The vulnerability identified as CVE-2016-2502 resides within the Qualcomm USB driver implementation in Android operating systems, specifically affecting devices such as the Nexus 5X and 6P prior to the security patch released on July 5, 2016. This flaw exists in the f_serial.c driver component which manages serial communication over USB gadget interfaces, creating a critical privilege escalation vector through improper input validation mechanisms. The vulnerability manifests when the GSER_IOCTL ioctl call receives an oversized parameter value, allowing malicious actors to exploit a buffer overflow condition that can be leveraged to execute arbitrary code with elevated privileges.
The technical implementation of this vulnerability stems from inadequate bounds checking within the USB gadget driver's ioctl handling routine. When the GSER_IOCTL command is processed, the driver fails to properly validate the size parameter passed in the ioctl call structure, enabling attackers to specify an excessively large buffer size that exceeds the allocated memory boundaries. This memory corruption vulnerability falls under the Common Weakness Enumeration category of CWE-121, which describes stack-based buffer overflow conditions where insufficient bounds checking allows data to overwrite adjacent memory locations. The flaw specifically represents a classic case of improper input validation that enables attackers to manipulate the driver's memory layout and potentially overwrite critical control structures or function pointers.
The operational impact of this vulnerability extends beyond simple privilege escalation to encompass potential system compromise and data exfiltration capabilities. Attackers who successfully exploit this vulnerability can gain root-level access to affected Android devices, enabling them to bypass security controls, install malicious applications, modify system files, and access sensitive user data. The exploitation requires minimal privileges since the vulnerability exists within the kernel-level USB driver component, making it particularly dangerous as it operates at the highest privilege level within the Android security model. This weakness directly violates the principle of least privilege and undermines the entire security architecture of the affected devices, as demonstrated by the fact that it was classified as an Android internal bug with identifier 27657963.
Mitigation strategies for CVE-2016-2502 involve immediate deployment of security patches released by Google and Qualcomm, which include proper input validation mechanisms and buffer size checks within the USB gadget driver. Organizations should implement comprehensive device management policies that ensure all Android devices receive timely security updates, particularly focusing on the specific kernel components affected by this vulnerability. The remediation approach aligns with the ATT&CK framework's defensive techniques for privilege escalation, emphasizing the importance of kernel-level patch management and input validation controls. System administrators should also consider implementing monitoring solutions that can detect anomalous ioctl call patterns and potentially indicate exploitation attempts, while maintaining regular vulnerability assessments to identify similar weaknesses in other kernel components that could serve as alternative attack vectors.