CVE-2017-5551 Explained : Impact and Mitigation
Learn about CVE-2017-5551 affecting the Linux kernel before version 4.9.6. Discover how local users can exploit the vulnerability to gain group privileges and the necessary mitigation steps.
CVE-2017-5551 was published on February 6, 2017, and affects the Linux kernel prior to version 4.9.6. This vulnerability allows local users to gain group privileges by exploiting a flaw in the simple_set_acl function.
Understanding CVE-2017-5551
CVE-2017-5551 is a security vulnerability in the Linux kernel that can be exploited by local users to elevate their privileges.
What is CVE-2017-5551?
The Linux kernel prior to version 4.9.6 has a function called simple_set_acl in fs/posix_acl.c that retains the setgid bit when performing a setxattr call on a tmpfs filesystem. This flaw can be exploited by local users who have access to a setgid program with limited execute permissions, granting them group privileges. It is important to note that this vulnerability is a result of an incomplete patch for CVE-2016-7097.
The Impact of CVE-2017-5551
The vulnerability allows local users to gain group privileges by leveraging the existence of a setgid program with restrictions on execute permissions.
Technical Details of CVE-2017-5551
CVE-2017-5551 affects the Linux kernel prior to version 4.9.6.
Vulnerability Description
The simple_set_acl function in fs/posix_acl.c in the Linux kernel before 4.9.6 preserves the setgid bit during a setxattr call involving a tmpfs filesystem, allowing local users to gain group privileges.
Affected Systems and Versions
- Affected System: Linux kernel prior to version 4.9.6
- Affected Versions: Not applicable
Exploitation Mechanism
Local users with access to a setgid program with limited execute permissions can exploit this vulnerability to elevate their privileges.
Mitigation and Prevention
It is crucial to take immediate steps to mitigate the impact of CVE-2017-5551 and prevent potential exploitation.
Immediate Steps to Take
- Apply relevant patches and updates provided by the Linux kernel maintainers.
- Restrict access to vulnerable systems to authorized personnel only.
Long-Term Security Practices
- Regularly monitor and audit user permissions and access rights.
- Implement the principle of least privilege to limit user capabilities.
Patching and Updates
- Keep the Linux kernel up to date with the latest security patches and fixes.