Vulnerability identifier: #VU9659

Vulnerability risk: High

CVSSv3.1: 9 [CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H/E:P/RL:O/RC:C]

CVE-ID: CVE-2017-17672

CWE-ID: CWE-502

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 weakness exists due to unsafe usage of PHP’s unserialize() on user-supplied input. A remote attacker can trigger a flaw in vB_Library_Template’s cacheTemplates() function, fetch information on a set of given templates from the database in order to store them inside a cache variable, delete arbitrary files and execute arbitrary code on a vBulletin installation.

Successful exploitation of the vulnerability may result in system compromise.

Mitigation
Install update from vendor's website.

Vulnerable software versions

vBulletin: 5.3.0 - 5.3.4

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External links
http://blogs.securiteam.com/index.php/archives/3573
http://forum.vbulletin.com/forum/vbulletin-announcements/vbulletin-announcements_aa/4383554-security-patch-released-for-vbulletin-5-3-2-5-3-3-and-5-3-4

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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?

No. We are not aware of malware exploiting this vulnerability. However, proof of concept for this vulnerability is available.