CVE-2018-12029 : Exploit Details and Defense Strategies
Learn about CVE-2018-12029 affecting Phusion Passenger 3.x through 5.x. Understand the privilege escalation risk and how to prevent unauthorized access to sensitive files.
Phusion Passenger 3.x through 5.x before version 5.3.2 in the nginx module is vulnerable to a race condition that can be exploited by a local attacker to gain elevated privileges.
Understanding CVE-2018-12029
In this CVE, a specific configuration vulnerability in Phusion Passenger allows an attacker to escalate privileges locally by manipulating file ownership.
What is CVE-2018-12029?
The vulnerability arises due to a race condition in the nginx module of Phusion Passenger, enabling a local attacker to exploit insufficiently strict permissions in a non-standard passenger_instance_registry_dir.
The Impact of CVE-2018-12029
This vulnerability can be leveraged by an attacker to gain elevated privileges, potentially leading to unauthorized access to sensitive files and data, such as the root's crontab file.
Technical Details of CVE-2018-12029
Phusion Passenger 3.x through 5.x before version 5.3.2 is affected by this vulnerability.
Vulnerability Description
A race condition in the nginx module of Phusion Passenger allows local privilege escalation by manipulating file ownership through symlink replacement.
Affected Systems and Versions
- Product: Phusion Passenger
- Versions affected: 3.x through 5.x before 5.3.2
Exploitation Mechanism
- Attacker configures a non-standard passenger_instance_registry_dir with insufficiently strict permissions.
- By replacing a file with a symlink before it is chowned, the attacker can manipulate the chown operation to affect the symlink target.
Mitigation and Prevention
To address CVE-2018-12029, follow these steps:
Immediate Steps to Take
- Upgrade Phusion Passenger to version 5.3.2 or later.
- Ensure strict permission settings on the passenger_instance_registry_dir.
Long-Term Security Practices
- Regularly monitor and audit file permissions and ownership.
- Implement the principle of least privilege to restrict access to sensitive files.
Patching and Updates
- Apply security patches and updates promptly to mitigate known vulnerabilities.