changedetection.io Vulnerable to Improper Input Validation Leading to LFR/Path Traversal

Summary

Improper input validation in the application can allow attackers to perform local file read (LFR) or path traversal attacks. These vulnerabilities occur when user input is used to construct file paths without adequate sanitization or validation. For example, using file:../../../etc/passwd or file: ///etc/passwd can bypass weak validations and allow unauthorized access to sensitive files. Even though this has been addressed in previous patch, it is still insufficient.

Details

The check in this line of code is insufficient.

if re.search(r'^file:/', url.strip(), re.IGNORECASE):

The attacker can still bypass this by using:
-file:../../../../etc/passwd
-file: ///etc/passwd (with space before /)

PoC

• Open up a changedetection.io instance with a webdriver configured.
• Create a new watch with file:../../../../etc/passwd.
• Check the watch preview.
• The contents of /etc/passwd should pop out.

Screenshots