CVE-2020-14304: Linux Kernel Information Disclosure Flaw

CVE-2020-14304 Overview

A memory disclosure flaw was found in the Linux kernel's ethernet drivers, in the way it read data from the EEPROM of the device. This vulnerability allows a local user to read uninitialized values from the kernel memory, potentially exposing sensitive information that should remain protected. The highest threat from this vulnerability is to confidentiality, as attackers with local access can leverage this flaw to extract kernel memory contents.

Critical Impact

Local users can read uninitialized kernel memory values through ethernet driver EEPROM operations, potentially exposing sensitive system information and compromising confidentiality.

Affected Products

• Linux Kernel version 4.9.210-1
• Linux Kernel version 4.19.118-2
• Linux Kernel version 5.6.7-1

Discovery Timeline

• 2020-09-15 - CVE-2020-14304 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2020-14304

Vulnerability Analysis

This vulnerability stems from improper handling of EEPROM data reading operations within the Linux kernel's ethernet device drivers. When the kernel reads data from the EEPROM of network devices, it fails to properly initialize memory buffers before use. This results in uninitialized memory being exposed to user space, constituting an information disclosure vulnerability.

The flaw is classified under CWE-460 (Improper Cleanup on Thrown Exception) and CWE-755 (Improper Handling of Exceptional Conditions), indicating that the root cause involves inadequate exception handling and resource cleanup during EEPROM read operations.

Root Cause

The vulnerability exists due to uninitialized memory use in the ethernet driver subsystem. When reading EEPROM data, the driver allocates memory buffers but does not zero-initialize them before populating with device data. If the EEPROM read operation fails partially or returns less data than expected, the remaining buffer space contains uninitialized kernel memory that gets exposed to the requesting user-space process.

Attack Vector

The attack requires local access to the target system with elevated privileges (high privileges required). An attacker can exploit this vulnerability by initiating EEPROM read operations through standard driver interfaces. The exploitation does not require user interaction and operates within the scope of the vulnerable component.

The attacker would typically interact with network device configuration interfaces or use specialized tools to trigger EEPROM reads. When the kernel fails to properly initialize or validate the data buffers, uninitialized memory contents leak to the attacker, potentially revealing kernel addresses, cryptographic material, or other sensitive data residing in kernel memory.

Detection Methods for CVE-2020-14304

Indicators of Compromise

• Unusual EEPROM read operations on ethernet devices by non-administrative processes
• Unexpected access patterns to network device configuration interfaces
• Memory access anomalies detected in kernel auditing subsystems
• Suspicious local process activity targeting ethernet driver interfaces

Detection Strategies

• Monitor system calls related to network device EEPROM operations using audit frameworks
• Implement kernel memory access logging to detect unauthorized memory disclosure attempts
• Deploy endpoint detection solutions capable of monitoring kernel-level driver interactions
• Review system logs for abnormal ethernet driver activity or repeated EEPROM access attempts

Monitoring Recommendations

• Enable comprehensive audit logging for privileged operations on network device interfaces
• Configure SELinux or AppArmor policies to restrict EEPROM access to authorized processes only
• Implement real-time alerting for kernel memory access violations
• Regularly review driver interaction logs for anomalous behavior patterns

How to Mitigate CVE-2020-14304

Immediate Actions Required

• Update the Linux kernel to a patched version that addresses this memory disclosure flaw
• Restrict local user access to systems running affected kernel versions
• Implement the principle of least privilege for users with local system access
• Monitor for exploitation attempts while awaiting patch deployment

Patch Information

Security patches addressing this vulnerability are available through Linux distribution channels. Administrators should consult their distribution's security advisories and apply kernel updates as they become available. Reference the Debian Bug Report #960702 and Red Hat Bugzilla CVE-2020-14304 for distribution-specific patch information and guidance.

Workarounds

• Restrict local access to affected systems to only trusted users with legitimate business needs
• Implement mandatory access control (MAC) policies to limit EEPROM read capabilities
• Use network namespaces to isolate ethernet driver access where applicable
• Consider disabling affected ethernet driver modules if alternative network connectivity is available

# Configuration example - Restrict access to ethernet device operations
# Add audit rules to monitor EEPROM-related system calls
auditctl -w /sys/class/net/ -p rwa -k ethernet_driver_access
auditctl -w /proc/net/ -p r -k network_proc_access

# Review audit logs for suspicious activity
ausearch -k ethernet_driver_access