CVE-2019-15791 Explained : Impact and Mitigation
Learn about CVE-2019-15791, a high-severity vulnerability in Ubuntu's 5.0 and 5.3 kernel series due to a reference count underflow in shiftfs. Find out the impact, affected systems, exploitation details, and mitigation steps.
Understanding CVE-2019-15791
What is CVE-2019-15791?
CVE-2019-15791 is a vulnerability found in the Ubuntu 5.0 and 5.3 kernel series due to the inclusion of shiftfs, a non-upstream patch in the Linux kernel. The issue arises from a function within shiftfs that fails to properly manage file references, leading to a refcount underflow.
The Impact of CVE-2019-15791
This vulnerability has a CVSS base score of 7.1, indicating a high severity level. It can result in a denial of service (DoS) attack due to a reference count underflow, potentially affecting the integrity of the system.
Technical Details of CVE-2019-15791
Vulnerability Description
The function shiftfs_btrfs_ioctl_fd_replace() in shiftfs does not correctly handle file references, causing a refcount underflow when closing file descriptors after a btrfs ioctl operation.
Affected Systems and Versions
- Product: Shiftfs in the Linux kernel
- Vendor: Ubuntu
- Affected Versions:
- 5.3.0-11.12 custom version
- 5.0 kernel custom version
Exploitation Mechanism
The vulnerability can be exploited locally with low privileges, impacting the availability and integrity of the system.
Mitigation and Prevention
Immediate Steps to Take
- Apply the patches provided by Ubuntu to address the vulnerability.
- Monitor security advisories for updates and follow best practices for secure kernel management.
Long-Term Security Practices
- Regularly update the kernel to the latest stable version.
- Implement proper file handling and reference management practices to prevent similar vulnerabilities.
Patching and Updates
- Update to the patched versions of the Ubuntu 5.0 and 5.3 kernel series to mitigate the vulnerability.