CVE-2018-9417 in Android
Summary
by MITRE • 11/20/2024
In f_hidg_read and hidg_disable of f_hid.c, there is a possible use-after-free due to improper locking. This could lead to local escalation of privilege with no additional execution privileges needed. User interaction is not needed for exploitation.
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Analysis
by VulDB Data Team • 11/20/2024
The vulnerability identified as CVE-2018-9417 resides within the USB gadget function driver implementation in the Linux kernel, specifically affecting the f_hid.c file which handles human interface device gadget functionality. This issue manifests in two primary functions: f_hidg_read and hidg_disable where improper locking mechanisms create conditions for use-after-free vulnerabilities to occur. The flaw exists in the kernel's USB gadget framework that allows USB devices to appear as host devices to computers, enabling various device emulation capabilities including HID devices like keyboards and mice.
The technical root cause stems from inadequate synchronization mechanisms within the USB gadget driver code where concurrent access to shared data structures occurs without proper locking protocols. When multiple threads or processes attempt to read from or disable the HID gadget functionality simultaneously, the lack of appropriate mutex or spinlock protection allows one thread to free memory resources while another thread attempts to access the same memory location, creating the use-after-free condition. This improper locking pattern falls under CWE-362 which specifically addresses race conditions and concurrent access issues in multi-threaded environments.
The operational impact of this vulnerability is significant as it enables local privilege escalation without requiring any additional execution privileges or user interaction. An attacker with local access to a system running affected kernel versions can exploit this flaw to elevate their privileges to root level, effectively compromising the entire system. The vulnerability is particularly dangerous because it operates entirely within the kernel space where the attacker can leverage the elevated privileges to gain complete control over system resources, access sensitive data, and potentially establish persistent backdoors. This type of attack aligns with ATT&CK technique T1068 which involves exploiting legitimate credentials and system access to escalate privileges.
The exploitation process involves triggering the race condition through concurrent operations on the HID gadget interface, causing the kernel to free memory structures while other operations attempt to reference them. This creates memory corruption that can be leveraged to execute arbitrary code with kernel-level privileges, bypassing standard user-space security controls. The vulnerability affects all Linux kernel versions that include the problematic f_hid.c implementation and requires no special user interaction or privileges to exploit, making it particularly dangerous in environments where local access is possible.
Mitigation strategies include applying the official kernel patches released by the Linux kernel security team which implement proper locking mechanisms around the affected functions. System administrators should prioritize updating to kernel versions containing the fix, typically kernel versions 4.17 and later which include the necessary synchronization improvements. Organizations should also implement monitoring solutions to detect unusual privilege escalation attempts and maintain regular kernel update schedules. Additional defensive measures include restricting local user access where possible and implementing kernel hardening techniques such as stack canaries and kernel address space layout randomization to make exploitation more difficult. The fix addresses the underlying concurrency issues by properly protecting shared resources with appropriate locking primitives, ensuring that memory operations occur in a synchronized manner that prevents the race conditions leading to the use-after-free vulnerability.