SB2020111904 - Arbitrary file upload in Backdrop CMS

Description

This security bulletin contains information about 1 security vulnerability.

1) Arbitrary file upload (CVE-ID: CVE-2020-13671)

The vulnerability allows a remote attacker to compromise vulnerable system.

The vulnerability exists due to insufficient validation of file during file upload. A remote attacker can upload a malicious PHP file and execute it on the server.

Additionally, it's recommended that you audit all previously uploaded files to check for malicious extensions. Look specifically for files that include more than one extension, like .php.txt or .html.gif. Pay specific attention to the following file extensions, which should be considered dangerous even when followed by another extension:

• phar
• php
• pl
• py
• cgi
• asp
• js
• html
• htm

Remediation

Install update from vendor's website.

References

• https://backdropcms.org/security/backdrop-sa-core-2020-007