CVE-2015-8816 in Linux
Summary
by MITRE
The hub_activate function in drivers/usb/core/hub.c in the Linux kernel before 4.3.5 does not properly maintain a hub-interface data structure, which allows physically proximate attackers to cause a denial of service (invalid memory access and system crash) or possibly have unspecified other impact by unplugging a USB hub device.
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Analysis
by VulDB Data Team • 07/26/2022
The vulnerability identified as CVE-2015-8816 resides within the Linux kernel's USB subsystem, specifically in the hub_activate function located in drivers/usb/core/hub.c. This flaw represents a critical memory management issue that affects systems running Linux kernel versions prior to 4.3.5. The vulnerability manifests when USB hub devices are physically disconnected from the system, creating a scenario where the kernel's USB hub interface data structure becomes corrupted or improperly maintained. The attack vector requires physical proximity to the target system, making it a local privilege escalation risk that can be exploited by attackers with physical access to the device. This type of vulnerability falls under the category of improper handling of resources, which is categorized as CWE-691 in the Common Weakness Enumeration taxonomy.
The technical flaw occurs due to inadequate synchronization and validation mechanisms within the hub activation process. When a USB hub is unplugged, the kernel's hub_activate function fails to properly update or invalidate the associated hub-interface data structure, leaving behind stale references or corrupted memory pointers. This improper memory management leads to invalid memory access patterns when the system attempts to reference the freed or corrupted data structure. The vulnerability can result in kernel panic conditions, system crashes, and complete denial of service for the affected system. The impact extends beyond simple system instability as the corrupted memory structures may potentially allow for more sophisticated attacks depending on the specific memory layout and system configuration. This vulnerability aligns with ATT&CK technique T1068 which involves exploiting local system vulnerabilities to gain elevated privileges or cause system instability.
The operational impact of CVE-2015-8816 is significant for organizations relying on Linux-based systems, particularly those in environments where physical security cannot be guaranteed. Attackers with physical access can exploit this vulnerability to disrupt system operations, potentially causing service interruptions, data loss, or system downtime. In critical infrastructure or embedded systems environments, this vulnerability could be leveraged to create persistent denial of service conditions that are difficult to detect and recover from. The vulnerability's exploitation requires minimal technical skill and can be automated, making it particularly dangerous in environments with unsecured physical access points. Organizations using older kernel versions are especially vulnerable as the fix requires kernel updates that may not be immediately available or deployable in all operational environments. The vulnerability demonstrates the importance of proper resource management in kernel-level code and highlights the need for thorough testing of device removal and reconnection scenarios. System administrators should prioritize updating to kernel versions 4.3.5 or later to mitigate this risk, as the patch addresses the core memory management issue by properly synchronizing access to hub interface data structures and ensuring proper cleanup during device removal operations.