Vulnerability identifier: #VU52635

Vulnerability risk: Critical

CVSSv3.1: 9.8 [CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:H/RL:U/RC:C]

CVE-ID: CVE-2021-20090

CWE-ID: CWE-22

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
WSR-2533DHPL2
Hardware solutions / Routers & switches, VoIP, GSM, etc
WSR-2533DHP3
Hardware solutions / Routers & switches, VoIP, GSM, etc

Vendor: BUFFALO INC.

Description

The vulnerability allows a remote attacker to perform directory traversal attacks.

The vulnerability exists due to input validation error when processing directory traversal sequences in the web interfaces. A remote attacker can send a specially crafted HTTP request and bypass authentication.

Note, the vulnerability is being exploited in-the-wild by the Mirai botnet in August 2021.

Mitigation
Cybersecurity Help is currently unaware of any official solution to address this vulnerability.

Vulnerable software versions

WSR-2533DHPL2: 1.02

WSR-2533DHP3: 1.24

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External links
http://www.tenable.com/security/research/tra-2021-13
http://medium.com/tenable-techblog/bypassing-authentication-on-arcadyan-routers-with-cve-2021-20090-and-rooting-some-buffalo-ea1dd30980c2

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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.