CVE-2018-18397 : Vulnerability Insights and Analysis

CVE-2018-18397 was published on December 12, 2018, and affects the Linux kernel prior to version 4.19.7. The vulnerability lies in the mishandling of access control for specific UFFDIO_ ioctl calls in the userfaultfd implementation, potentially allowing local users to write data into empty spaces within a tmpfs file.

Understanding CVE-2018-18397

This CVE entry highlights a security flaw in the Linux kernel that could be exploited by local users under specific conditions.

What is CVE-2018-18397?

The vulnerability in the userfaultfd implementation allows local users to write data into holes in a tmpfs file, provided the user has read-only access to the file and the file contains such empty spaces. The issue is related to the files fs/userfaultfd.c and mm/userfaultfd.c.

The Impact of CVE-2018-18397

The mishandling of access control for UFFDIO_ ioctl calls can lead to unauthorized data manipulation by local users, potentially compromising the integrity of files within the system.

Technical Details of CVE-2018-18397

This section delves into the specifics of the vulnerability.

Vulnerability Description

The userfaultfd implementation in the Linux kernel before version 4.19.7 mishandles access control for certain UFFDIO_ ioctl calls, allowing local users to write data into holes in a tmpfs file.

Affected Systems and Versions

Affected System: Linux kernel prior to version 4.19.7
Affected Component: userfaultfd implementation

Exploitation Mechanism

The vulnerability can be exploited by local users with read-only access to a file containing empty spaces within a tmpfs file.

Mitigation and Prevention

Protecting systems from CVE-2018-18397 requires immediate actions and long-term security practices.

Immediate Steps to Take

Apply relevant patches and updates to the Linux kernel to mitigate the vulnerability.
Monitor and restrict user access to critical files and directories.

Long-Term Security Practices

Implement the principle of least privilege to limit user capabilities.
Regularly review and update access control policies to prevent unauthorized data manipulation.

Patching and Updates

Update the Linux kernel to version 4.19.7 or newer to address the access control issue in the userfaultfd implementation.