Arbitrary File Write via Archive Extraction (Zip Slip)

Affecting microweber/microweber package, versions <1.2.0.x-dev

Overview

microweber/microweber is a new generation CMS with drag and drop.

Affected versions of this package are vulnerable to Arbitrary File Write via Archive Extraction (Zip Slip). A directory traversal issue in the Utils/Unzip module allows an authenticated attacker to gain remote code execution via the backup restore feature. To exploit the vulnerability, an attacker must have the credentials of an administrative user, upload a maliciously constructed ZIP file with file paths including relative paths (i.e., ../../), move this file into the backup directory, and execute a restore on this file.

Details

It is exploited using a specially crafted zip archive, that holds path traversal filenames. When exploited, a filename in a malicious archive is concatenated to the target extraction directory, which results in the final path ending up outside of the target folder. For instance, a zip may hold a file with a "../../file.exe" location and thus break out of the target folder. If an executable or a configuration file is overwritten with a file containing malicious code, the problem can turn into an arbitrary code execution issue quite easily.

The following is an example of a zip archive with one benign file and one malicious file. Extracting the malicous file will result in traversing out of the target folder, ending up in /root/.ssh/ overwriting the authorized_keys file:

+2018-04-15 22:04:29 ..... 19 19 good.txt

+2018-04-15 22:04:42 ..... 20 20 ../../../../../../root/.ssh/authorized_keys

Remediation

Upgrade microweber/microweber to version 1.2.0.x-dev or higher.

References

• Blog Post
• GitHub Commit