CVE-2020-0404: Android Kernel Privilege Escalation Flaw

CVE-2020-0404 Overview

CVE-2020-0404 is a local privilege escalation vulnerability in the Linux kernel's USB Video Class (UVC) driver, specifically within the uvc_scan_chain_forward function in uvc_driver.c. The vulnerability stems from a linked list corruption issue that can lead to local privilege escalation in the kernel without requiring any additional execution privileges. Notably, user interaction is not needed for exploitation, making this vulnerability particularly concerning for systems with USB device exposure.

Critical Impact

Local attackers can exploit linked list corruption in the UVC driver to escalate privileges to kernel level without user interaction, potentially gaining complete control over affected Android devices and Oracle cloud-native core products.

Affected Products

• Google Android (all kernel versions)
• Oracle Communications Cloud Native Core Binding Support Function 22.1.3
• Oracle Communications Cloud Native Core Network Exposure Function 22.1.1
• Oracle Communications Cloud Native Core Policy 22.2.0

Discovery Timeline

• September 17, 2020 - CVE-2020-0404 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2020-0404

Vulnerability Analysis

The vulnerability resides in the uvc_scan_chain_forward function within the Linux kernel's UVC (USB Video Class) driver implementation. This function is responsible for scanning and managing video streaming chain descriptors when USB video devices are connected to the system.

The flaw involves improper handling of linked list structures during the forward scanning process of UVC device chains. When processing malformed or specially crafted USB video device descriptors, the driver fails to properly validate and maintain linked list integrity, leading to list corruption. This corruption can subsequently be leveraged to achieve privilege escalation from a local context to kernel-level privileges.

The attack requires local access to the system but does not require elevated privileges to initiate. Since no user interaction is needed for exploitation, an attacker with physical access to USB ports or the ability to present malicious USB devices could potentially trigger this vulnerability automatically.

Root Cause

The root cause is categorized under CWE-269 (Improper Privilege Management), though the underlying technical issue involves linked list corruption due to an unusual handling condition in the UVC driver's chain scanning logic. The driver does not properly handle edge cases when traversing video streaming unit chains, allowing list pointers to be corrupted under specific conditions.

Attack Vector

The attack vector is local, requiring an attacker to have local access to the target system. The exploitation scenario typically involves:

1. An attacker connects or emulates a malicious USB video device to the target system
2. The kernel's UVC driver automatically processes the device descriptors
3. During the chain forward scanning process, specially crafted descriptors trigger the linked list corruption
4. The corrupted list structures are leveraged to manipulate kernel memory
5. Privilege escalation from the attacker's context to kernel-level privileges is achieved

The vulnerability is particularly dangerous in Android environments where USB accessories are commonly connected, and in virtualized Oracle cloud environments where USB passthrough may be configured.

Detection Methods for CVE-2020-0404

Indicators of Compromise

• Unusual kernel oops or panic messages related to the UVC driver or uvc_scan_chain_forward function
• Unexpected USB video device enumeration events in system logs
• Kernel memory corruption signs in dmesg output referencing linked list operations
• Suspicious processes running with elevated privileges after USB device connections

Detection Strategies

• Monitor kernel logs for UVC driver errors, particularly messages containing uvc_scan_chain_forward or linked list corruption warnings
• Implement USB device whitelisting to control which USB video devices can connect to systems
• Deploy endpoint detection and response (EDR) solutions capable of monitoring kernel-level activities and privilege escalation attempts
• Utilize SentinelOne's behavioral AI to detect anomalous privilege transitions following USB device events

Monitoring Recommendations

• Enable verbose logging for USB subsystem events on critical systems
• Configure alerting for unexpected kernel module loading or USB device enumeration
• Monitor for processes spawned with kernel privileges that originated from non-privileged contexts
• Review system audit logs for changes in user privilege levels coinciding with USB activity

How to Mitigate CVE-2020-0404

Immediate Actions Required

• Apply the latest Android security patches from the September 2020 security bulletin
• Update Oracle Communications Cloud Native Core products to patched versions as specified in Oracle's July 2022 CPU
• Restrict physical USB access on sensitive systems where possible
• Consider disabling UVC driver loading on systems that do not require USB video functionality

Patch Information

Google addressed this vulnerability in the Android Security Bulletin September 2020. The fix was also integrated into upstream kernel releases. Oracle released patches for affected Communications Cloud Native Core products in the Oracle CPU July 2022 Security Alert. Additional patches for openSUSE distributions were released in October 2020.

For Android devices, ensure the security patch level is September 2020 or later. For Oracle products, apply the patches referenced in the July 2022 Critical Patch Update.

Workarounds

• Blacklist the uvcvideo kernel module on systems that do not require USB webcam functionality by adding blacklist uvcvideo to /etc/modprobe.d/blacklist.conf
• Implement USB device authorization policies using udev rules to prevent automatic loading of USB video devices
• Deploy USB port blocking hardware or software controls on high-security systems
• Use virtualization or containerization to isolate USB device access from critical system components

# Configuration example - Blacklist UVC driver to prevent automatic loading
echo "blacklist uvcvideo" | sudo tee /etc/modprobe.d/blacklist-uvc.conf
sudo update-initramfs -u

# Alternative: Disable USB video device authorization via udev
echo 'SUBSYSTEM=="usb", ATTR{bDeviceClass}=="0e", ATTR{authorized}="0"' | sudo tee /etc/udev/rules.d/99-block-uvc.rules
sudo udevadm control --reload-rules