Vulnerability identifier: #VU42751

Vulnerability risk: High

CVSSv3.1: 9.4 [CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:H/RL:O/RC:C]

CVE-ID: CVE-2020-17496

CWE-ID: CWE-94

Exploitation vector: Network

Exploit availability: Yes

Vulnerable software:
vBulletin
Web applications / Forum & blogging software

Vendor: vBulletin

Description

The vulnerability allows a remote attacker to execute arbitrary code on the target system.

The vulnerability exists due to improper input validation when processing untrused input passed via the "subWidgets[0][config][code]" HTTP parameter to "/ajax/render/widget_tabbedcontainer_tab_panel" URL. A remote attacker can send a specially crafted request and execute arbitrary PHP code on the target system.

Successful exploitation of this vulnerability may result in complete compromise of vulnerable system.

Exploitation example:

curl -s http://SITE/ajax/render/widget_tabbedcontainer_tab_panel -d 'subWidgets[0][template]=widget_php&subWidgets[0][config][code]=echo shell_exec("id"); exit;'

Mitigation
Install updates from vendor's website.

Vulnerable software versions

vBulletin: 5.6.0 - 5.6.2

---

External links
http://forum.vbulletin.com/forum/vbulletin-announcements/vbulletin-announcements_aa/4445227-vbulletin-5-6-0-5-6-1-5-6-2-security-patch
http://blog.exploitee.rs/2020/exploiting-vbulletin-a-tale-of-patch-fail/

---

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?

Yes. This vulnerability is being exploited in the wild.