CVE-2020-14390 in Linux
Summary
by MITRE
A flaw was found in the Linux kernel in versions from 2.2.3 through 5.9.rc5. When changing screen size, an out-of-bounds memory write can occur leading to memory corruption or a denial of service. This highest threat from this vulnerability is to system availability.
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Analysis
by VulDB Data Team • 09/19/2020
The vulnerability described in CVE-2020-14390 represents a critical memory corruption flaw within the Linux kernel that affects a wide range of kernel versions from 2.2.3 through 5.9.rc5. This issue manifests specifically during screen size changes, indicating a direct relationship between display management operations and kernel memory handling. The vulnerability falls under the category of out-of-bounds memory write conditions, which are particularly dangerous because they can lead to unpredictable system behavior and potential exploitation by malicious actors. The flaw operates at the kernel level, making it especially severe as it can compromise the fundamental operating system integrity.
The technical implementation of this vulnerability stems from improper bounds checking during screen dimension modifications within the kernel's graphics subsystem. When a user or application attempts to change screen parameters, the kernel fails to validate the input values against allocated memory boundaries, resulting in data being written beyond the intended memory allocation. This type of vulnerability maps directly to CWE-787, which specifically addresses out-of-bounds write conditions in software implementations. The memory corruption can manifest in various ways including system crashes, data corruption, or potentially more severe consequences depending on the execution context where the flaw occurs.
The operational impact of CVE-2020-14390 extends beyond simple denial of service scenarios, as the memory corruption can potentially be exploited to gain unauthorized access to system resources or cause persistent system instability. The vulnerability's classification as having the highest threat to system availability indicates that successful exploitation could lead to complete system shutdowns or reboot cycles, affecting system reliability and uptime. From an attack perspective, this flaw aligns with ATT&CK technique T1068, which involves local privilege escalation through kernel exploits, and T1499, which encompasses network denial of service attacks that can leverage kernel vulnerabilities to disrupt system operations.
Mitigation strategies for this vulnerability primarily focus on immediate kernel version updates to patched releases beyond 5.9.rc5, as well as implementing proper input validation mechanisms within the graphics subsystem. System administrators should prioritize patching affected systems, particularly those running older kernel versions from the 2.2.3 to 5.9.rc5 range. Additional protective measures include monitoring for unusual screen size change operations that might indicate exploitation attempts and implementing kernel hardening techniques such as stack canaries and address space layout randomization. The vulnerability also underscores the importance of comprehensive testing for kernel memory management functions and the need for robust bounds checking mechanisms in all system-level operations that manipulate display parameters or handle user input within kernel space.