Improper authentication in Dropbear

1) Improper authentication

EUVDB-ID: #VU79726

Risk: Medium

CVSSv3.1: 4.7 [CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N/E:U/RL:O/RC:C]

CVE-ID: CVE-2021-36369

CWE-ID: CWE-287 - Improper Authentication

Exploit availability: No

Description

The vulnerability allows a remote user to bypass authentication process.

The vulnerability exists due to a non-RFC-compliant check of the available authentication methods in the client-side SSH code. A remote user can bypass additional security measures such as FIDO2 tokens or SSH-Askpass and abuse a forwarded agent for logging on to another server unnoticed.

Mitigation

Install updates from vendor's website.

Vulnerable software versions

Dropbear: 2011.54 - 2020.81

External links

http://github.com/mkj/dropbear/pull/128
http://github.com/mkj/dropbear/releases/tag/DROPBEAR_2022.82
http://lists.debian.org/debian-lts-announce/2022/11/msg00015.html

Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote authenticated user 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.