Vulnerability identifier: #VU300

Vulnerability risk: Critical

CVSSv3.1: 9.5 [CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H/E:H/RL:O/RC:C]

CVE-ID: CVE-2016-6483

CWE-ID: CWE-918

Exploitation vector: Network

Exploit availability: Yes

Vulnerable software:
vBulletin
Web applications / Forum & blogging software

Vendor: vBulletin

Description

The vulnerability allows a remote attacker to perform server-side forgery attacks and compromise vulnerable system.

The vulnerability exists due to incorrect link handling in file upload functionality. A remote attacker can use a malicious server that returns a 301 HTTP redirect response to local resource to connect to services within internal network or on localhost.

Successful exploitation of this vulnerability may allow an attacker to perform SSRF attack to retrieve information for further attacks against vulnerable system by performing unauthorized connections to local resources, gain access to sensitive information and compromise vulnerable system.

Note: this vulnerability is being actively exploited in the wild.

Mitigation
To resolve this issue install security patch from vendor's website:

5.2.2 Patch Level 1
5.2.1 Patch Level 1
5.2.0 Patch Level 3

4.2.3 Patch Level 2
4.2.2 Patch Level 6

3.8.9 Patch Level 1
3.8.8 Patch Level 2
3.8.7 Patch Level 6

Vulnerable software versions

vBulletin: 3.8.7 - 5.2.2

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External links
http://www.vbulletin.com/forum/forum/vbulletin-announcements/vbulletin-announcements_aa/4349551-secu...
http://legalhackers.com/advisories/vBulletin-SSRF-Vulnerability-Exploit.txt
http://www.vbulletin.com/forum/forum/vbulletin-announcements/vbulletin-announcements_aa/4349548-secu...
http://www.vbulletin.com/forum/forum/vbulletin-announcements/vbulletin-announcements_aa/4349549-secu...

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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.