CVE-2020-14390 Overview
A flaw was found in the Linux kernel in versions before 5.9-rc6. When changing screen size, an out-of-bounds memory write can occur leading to memory corruption or a denial of service. Due to the nature of the flaw, privilege escalation cannot be fully ruled out.
Critical Impact
This out-of-bounds write vulnerability in the Linux kernel can lead to memory corruption, denial of service, and potential privilege escalation when screen size changes are triggered on affected systems.
Affected Products
- Linux Kernel versions before 5.9-rc6
- Linux Kernel 5.9.0 release candidates (rc1 through rc5)
- Debian Linux 9.0
Discovery Timeline
- September 18, 2020 - CVE-2020-14390 published to NVD
- November 21, 2024 - Last updated in NVD database
Technical Details for CVE-2020-14390
Vulnerability Analysis
This vulnerability (CWE-787: Out-of-bounds Write) exists in the Linux kernel's screen size handling functionality. When a screen size change operation is performed, the kernel fails to properly validate memory boundaries, resulting in an out-of-bounds memory write condition. This type of vulnerability can corrupt adjacent memory regions, potentially affecting kernel data structures and system stability.
The local attack vector requires an attacker to have high privileges on the target system. Once exploited, the vulnerability can compromise system integrity and availability, with limited impact on confidentiality. While primarily manifesting as a denial of service condition, the memory corruption nature of the flaw means that privilege escalation scenarios cannot be entirely dismissed.
Root Cause
The root cause of this vulnerability lies in improper bounds checking during screen resize operations within the Linux kernel. When the screen dimensions are modified, the kernel performs memory operations to accommodate the new size. However, insufficient validation of these new dimensions allows writes to occur beyond the allocated buffer boundaries, leading to out-of-bounds memory access.
Attack Vector
The vulnerability requires local access to the system with elevated privileges. An attacker with appropriate permissions can trigger the vulnerability by initiating a screen size change operation that causes the kernel to write data beyond allocated memory boundaries. The attack does not require user interaction once the attacker has the necessary local access.
The exploitation scenario involves manipulating screen dimension parameters to trigger improper memory writes. While the immediate consequence is memory corruption leading to system instability or denial of service, the corrupted memory regions could potentially be leveraged for more sophisticated attacks depending on system configuration and memory layout.
Detection Methods for CVE-2020-14390
Indicators of Compromise
- Unexpected kernel panics or system crashes during display or terminal operations
- Memory corruption errors in kernel logs related to framebuffer or console subsystems
- Unusual system instability when screen dimensions are changed
- Kernel oops messages referencing out-of-bounds memory access
Detection Strategies
- Monitor system logs for kernel panic events associated with display or console operations
- Implement kernel debugging tools to detect out-of-bounds memory access patterns
- Deploy endpoint detection solutions capable of monitoring kernel-level memory operations
- Review audit logs for unusual privilege escalation attempts following system instability
Monitoring Recommendations
- Enable kernel crash dump analysis to identify root causes of unexpected system failures
- Configure alerting for repeated kernel errors related to memory access violations
- Monitor affected Linux systems for signs of exploitation attempts during maintenance windows
- Track vendor security advisories from Red Hat, Debian, and openSUSE
How to Mitigate CVE-2020-14390
Immediate Actions Required
- Update the Linux kernel to version 5.9-rc6 or later to address this vulnerability
- Apply distribution-specific security patches from your Linux vendor
- Review system access controls to limit local privileged access to authorized personnel only
- Implement kernel security hardening measures where available
Patch Information
Security patches addressing this vulnerability have been released by multiple Linux distributions. Administrators should consult their distribution's security advisories for specific patch versions:
Workarounds
- Restrict local access to systems running vulnerable kernel versions
- Limit privileged user access to only essential administrative personnel
- Consider implementing additional access controls on display and console operations where possible
- Deploy endpoint protection solutions to monitor for exploitation attempts while patches are being applied
# Check current kernel version
uname -r
# For Debian-based systems, update to patched kernel
sudo apt update && sudo apt upgrade linux-image-$(uname -r)
# For RHEL/CentOS systems
sudo yum update kernel
# Reboot to apply kernel update
sudo reboot
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
