CVE-2015-7833 in Red Hat
Summary
by MITRE
The usbvision driver in the Linux kernel package 3.10.0-123.20.1.el7 through 3.10.0-229.14.1.el7 in Red Hat Enterprise Linux (RHEL) 7.1 allows physically proximate attackers to cause a denial of service (panic) via a nonzero bInterfaceNumber value in a USB device descriptor.
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Analysis
by VulDB Data Team • 06/22/2022
The usbvision driver vulnerability identified as CVE-2015-7833 represents a critical denial of service flaw within the Linux kernel's USB subsystem that affects Red Hat Enterprise Linux 7.1 versions ranging from 3.10.0-123.20.1.el7 through 3.10.0-229.14.1.el7. This vulnerability resides in the kernel's USB device handling mechanisms and specifically targets the usbvision driver module responsible for managing certain USB video devices. The flaw manifests when the driver encounters a USB device descriptor containing a nonzero bInterfaceNumber field value, which triggers an unexpected kernel panic condition. The vulnerability's impact is particularly concerning because it can be exploited by attackers who are physically present near the affected system, making it a significant concern for environments where physical security cannot be guaranteed.
The technical root cause of this vulnerability stems from inadequate input validation within the usbvision driver's device descriptor parsing logic. When a USB device connects to the system, the kernel's USB subsystem reads the device descriptor to understand the device's capabilities and configuration. The bInterfaceNumber field in the USB device descriptor is supposed to identify which interface of a USB device is being referenced, and according to USB specifications, this value should typically be zero for the first interface. However, the vulnerable driver code fails to properly validate or handle cases where this field contains a nonzero value, leading to a kernel panic when the driver attempts to process such malformed descriptors. This behavior aligns with CWE-129, which describes improper validation of input ranges, and represents a classic example of insufficient bounds checking in kernel space code.
The operational impact of this vulnerability extends beyond simple denial of service, as it can result in complete system crashes that require manual intervention to restore normal operation. When exploited, the vulnerability causes the kernel to panic and halt system operations, potentially leading to data loss and service disruption in mission-critical environments. The physical proximity requirement for exploitation limits the attack surface but does not eliminate the threat, particularly in shared workspaces, data centers, or environments where unauthorized physical access is possible. From an attack perspective, this vulnerability maps to ATT&CK technique T1059.001, which covers command and script injection, as attackers can leverage physical access to introduce malicious USB devices that trigger the kernel panic. The vulnerability also represents a potential vector for persistent attacks where an attacker might repeatedly exploit the system to maintain control through repeated system reboots.
Mitigation strategies for CVE-2015-7833 should focus on both immediate patching and operational security measures. The primary solution involves applying the relevant kernel security patches provided by Red Hat, which typically include enhanced input validation for USB device descriptors within the usbvision driver module. Organizations should prioritize updating their RHEL 7.1 systems to versions that contain the fix, as the vulnerability remains exploitable in unpatched systems. Additionally, implementing USB device whitelisting policies and disabling unnecessary USB interfaces can significantly reduce the attack surface. Network administrators should also consider implementing physical security controls such as USB port locking mechanisms or restricted access areas to prevent unauthorized physical access to systems. The vulnerability highlights the importance of kernel security hardening practices and proper input validation in device driver code, particularly in kernel space where errors can lead to complete system compromise. Organizations should also conduct regular security assessments of their USB device management policies and ensure that security updates are applied promptly to maintain system integrity and prevent exploitation of similar vulnerabilities in the future.