CVE-2016-4482 in Android
Summary
by MITRE
The proc_connectinfo function in drivers/usb/core/devio.c in the Linux kernel through 4.6 does not initialize a certain data structure, which allows local users to obtain sensitive information from kernel stack memory via a crafted USBDEVFS_CONNECTINFO ioctl call.
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Analysis
by VulDB Data Team • 09/12/2022
The vulnerability identified as CVE-2016-4482 represents a critical information disclosure flaw within the Linux kernel's USB subsystem that affects versions through 4.6. This issue resides in the proc_connectinfo function located in drivers/usb/core/devio.c, where a specific data structure fails to undergo proper initialization before being populated with information. The vulnerability manifests when a local attacker executes a crafted USBDEVFS_CONNECTINFO ioctl call, enabling them to extract sensitive data that may have been previously stored in kernel memory. This particular flaw falls under the category of information disclosure vulnerabilities as defined by CWE-200, where an attacker can access data that should remain confidential. The root cause stems from inadequate input validation and memory management practices within the kernel's USB device interface implementation, creating a pathway for unauthorized data retrieval from kernel stack memory regions.
The technical exploitation of this vulnerability requires local system access and leverages the USBDEVFS_CONNECTINFO ioctl command which is designed to provide connection information about USB devices. When the proc_connectinfo function processes this ioctl call, it fails to properly initialize a data structure before populating it with values from kernel memory. This incomplete initialization results in the exposure of uninitialized memory contents, including potentially sensitive kernel data, stack contents, or remnants of previous operations that may contain credentials, cryptographic keys, or other confidential information. The vulnerability demonstrates a classic example of uninitialized variable usage that can lead to information leakage, a pattern commonly referenced in security best practices and addressed by the CWE-457 standard for use of uninitialized variables. Attackers can repeatedly exploit this flaw to gather increasingly detailed information about the kernel state, potentially enabling more sophisticated attacks or further privilege escalation attempts.
The operational impact of CVE-2016-4482 extends beyond simple information disclosure, as the leaked kernel memory may contain sensitive data that could be exploited in conjunction with other vulnerabilities. Local attackers who gain access to kernel memory contents can potentially extract cryptographic keys, session tokens, or other confidential information that could be used for privilege escalation or system compromise. This vulnerability is particularly concerning in multi-user environments where local access might be obtained through social engineering, compromised accounts, or other attack vectors. The exposure of kernel stack memory contents also violates fundamental security principles of information hiding and memory protection that are core to operating system security models. From an attack framework perspective, this vulnerability aligns with techniques described in the ATT&CK framework under the information gathering phase, where adversaries collect system information to inform subsequent attack steps. The vulnerability affects systems running Linux kernel versions 4.6 and earlier, making it relevant for organizations maintaining older kernel versions or those that have not yet applied the necessary security patches.
Mitigation strategies for CVE-2016-4482 focus primarily on kernel updates and system hardening measures. The most effective remediation involves upgrading to Linux kernel versions 4.7 or later, where the vulnerability has been addressed through proper initialization of the affected data structure. System administrators should implement regular patch management procedures to ensure all kernel components remain current with security fixes. Additional mitigations include restricting local user access where possible, implementing proper access controls for USB device interfaces, and monitoring for suspicious USBDEVFS_CONNECTINFO ioctl usage patterns. Organizations should also consider implementing kernel hardening techniques such as stack canaries, kernel address space layout randomization, and other exploit mitigation strategies. The vulnerability highlights the importance of thorough code review processes and proper memory management practices in kernel development, emphasizing the need for comprehensive testing of kernel subsystems before deployment. Security monitoring should include detection of unauthorized USB device access patterns and potential exploitation attempts targeting kernel memory disclosure vulnerabilities.