Source: cve@mitre.org
ez-ipupdate 3.0.11b7 and earlier creates insecure temporary cache files, which allows local users to conduct unauthorized operations via a symlink attack on the ez-ipupdate.cache file.
ez-ipupdate versions 3.0.11b7 and earlier are vulnerable to a symlink attack, allowing local attackers to overwrite the ez-ipupdate.cache file and potentially execute arbitrary commands. This vulnerability can lead to privilege escalation and compromise of the system's integrity, enabling unauthorized access and control.
Step 1: Preparation: The attacker creates a symbolic link named ez-ipupdate.cache that points to a target file (e.g., /etc/passwd).
Step 2: Triggering the Update: The attacker triggers ez-ipupdate to run, typically by waiting for the scheduled update or manually invoking the command.
Step 3: File Overwrite: ez-ipupdate attempts to write to ez-ipupdate.cache. Because it's a symlink, the write operation actually modifies the target file (e.g., /etc/passwd).
Step 4: Privilege Escalation/System Compromise: The attacker crafts the data written to the target file to achieve their goal, such as adding a user with elevated privileges or injecting malicious code.
The vulnerability stems from the insecure creation of the ez-ipupdate.cache file. The software does not properly validate or secure the creation of this temporary file. An attacker can exploit this by creating a symbolic link pointing to a critical system file (e.g., /etc/passwd or a script executed by root). When ez-ipupdate writes to the ez-ipupdate.cache file, it actually writes to the target of the symlink, allowing the attacker to overwrite the target file. The root cause is a lack of input validation and secure file handling, specifically the failure to check if the target file is a symbolic link or to use a temporary file with a unique, predictable name. This results in a race condition where the attacker can manipulate the file system before ez-ipupdate writes to the cache.
While no specific APT groups are known to have specifically targeted this vulnerability, its simplicity and potential for privilege escalation make it attractive for various attackers. This vulnerability is not listed on the CISA KEV list, but it's important to note that its age and simplicity make it a potential target for opportunistic attacks.
Monitor file system activity for the creation of symlinks, especially those named ez-ipupdate.cache or pointing to sensitive system files.
Analyze system logs for unusual activity related to ez-ipupdate, such as unexpected errors or modifications to critical files.
Implement file integrity monitoring to detect changes to critical system files like /etc/passwd, /etc/shadow, and scripts executed by root.
Network monitoring for unusual DNS update requests, although this is less relevant to the local nature of the exploit.
Upgrade to a patched version of ez-ipupdate (3.0.11b8 or later).
Implement file system security measures, such as restricting write access to sensitive files and directories.
Regularly audit system configurations and file permissions.
Use a file integrity monitoring tool to detect unauthorized changes to critical files.
If upgrading is not possible, consider removing or disabling ez-ipupdate if it's not essential for the system's functionality.