MitM attack in PuTTY

1) Man-in-the-Middle (MitM) attack

EUVDB-ID: #VU29487

Risk: Medium

CVSSv4.0: 1 [CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:U/U:Green]

CVE-ID: CVE-2020-14002

CWE-ID: CWE-300 - Channel Accessible by Non-Endpoint ('Man-in-the-Middle')

Exploit availability: No

Description

The vulnerability allows a remote attacker to perform a Man-in-the-Middle (MitM) attack.

The vulnerability exists due to an observable discrepancy issue in the algorithm negotiation. This allows man-in-the-middle attackers to target initial connection attempts (where no host key for the server has been cached by the client).

Mitigation

Install updates from vendor's website.

Vulnerable software versions

PuTTY: 0.68 - 0.73

CPE2.3

• cpe:2.3:a:simon_tatham:putty:0.68:*:*:*:*:*:*:*
• cpe:2.3:a:simon_tatham:putty:0.69:*:*:*:*:*:*:*
• cpe:2.3:a:simon_tatham:putty:0.70:*:*:*:*:*:*:*

External links

https://lists.tartarus.org/pipermail/putty-announce/
https://www.chiark.greenend.org.uk/~sgtatham/putty/changes.html
https://www.fzi.de/en/news/news/detail-en/artikel/fsa-2020-2-ausnutzung-eines-informationslecks-fuer-gezielte-mitm-angriffe-auf-ssh-clients/

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.