MitM attack in OpenSSH client

1) Use of a broken or risky cryptographic algorithm

EUVDB-ID: #VU32937

Risk: Medium

CVSSv3.1: 4.8 [CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N/E:U/RL:W/RC:C]

CVE-ID: CVE-2020-14145

CWE-ID: CWE-327 - Use of a Broken or Risky Cryptographic Algorithm

Exploit availability: No

Description

The vulnerability allows a remote attacker to perform MitM attack.

The vulnerability exists in openssh client during algorithm negotiation due to observable discrepancy. A remote attacker can perform a Man-in-the-Middle (MitM) attack.

Mitigation

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

Partial mitigation against this issue was included in OpenSSH 8.4

Vulnerable software versions

OpenSSH: 5.7 - 8.3p1

External links

http://github.com/openssh/openssh-portable/compare/V_8_3_P1...V_8_4_P1
http://security.netapp.com/advisory/ntap-20200709-0004/
http://www.fzi.de/en/news/news/detail-en/artikel/fsa-2020-2-ausnutzung-eines-informationslecks-fuer-gezielte-mitm-angriffe-auf-ssh-clients/
http://anongit.mindrot.org/openssh.git/commit/?id=b3855ff053f5078ec3d3c653cdaedefaa5fc362d

Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the local network (LAN).

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.