Arbitrary file upload in Backdrop CMS

1) Arbitrary file upload

EUVDB-ID: #VU48540

Risk: High

CVSSv3.1: 8.5 [CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C]

CVE-ID: CVE-2020-13671

CWE-ID: CWE-434 - Unrestricted Upload of File with Dangerous Type

Exploit availability: No

Description

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

Mitigation

Install update from vendor's website.

Vulnerable software versions

Backdrop CMS: 1.15.0 - 1.17.2

External links

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

Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.