Remote code execution in FortiWeb Proxyd

1) Stack-based buffer overflow

EUVDB-ID: #VU84879

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-2021-42756

CWE-ID: CWE-121 - Stack-based buffer overflow

Exploit availability: No

Description

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

The vulnerability exists due to a boundary error in the proxy daemon. A remote unauthenticated attacker can send a specially crafted HTTP request to the system, trigger a stack-based buffer overflow and execute arbitrary code on the target system.

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

Mitigation

Install updates from vendor's website.

Vulnerable software versions

Fortinet FortiWeb: 5.6.0 - 6.4.2

CPE2.3

• cpe:2.3:a:fortinet:fortinet_fortiweb:6.4.2:*:*:*:*:*:*:*
• cpe:2.3:a:fortinet:fortinet_fortiweb:6.3.16:*:*:*:*:*:*:*
• cpe:2.3:a:fortinet:fortinet_fortiweb:6.2.6:*:*:*:*:*:*:*
• cpe:2.3:a:fortinet:fortinet_fortiweb:5.7.3:*:*:*:*:*:*:*
• cpe:2.3:a:fortinet:fortinet_fortiweb:5.8.7:*:*:*:*:*:*:*
• cpe:2.3:a:fortinet:fortinet_fortiweb:6.0.7:*:*:*:*:*:*:*
• cpe:2.3:a:fortinet:fortinet_fortiweb:6.1.2:*:*:*:*:*:*:*
• cpe:2.3:a:fortinet:fortinet_fortiweb:5.9.1:*:*:*:*:*:*:*
• cpe:2.3:a:fortinet:fortinet_fortiweb:5.6.2:*:*:*:*:*:*:*

External links

http://www.fortiguard.com/psirt/FG-IR-21-186

Q & A

Can this vulnerability be exploited remotely?

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

How the attacker can exploit this vulnerability?

The attacker would have to send a specially crafted request to the affected application in order to exploit this vulnerability.

Is there known malware, which exploits this vulnerability?

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