#VU55005 Insufficient verification of data authenticity in PuTTY - CVE-2021-36367

Vulnerability identifier: #VU55005

Vulnerability risk: Medium

CVSSv4.0: 4.6 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:U/U:Green]

CVE-ID: CVE-2021-36367

CWE-ID: CWE-345

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
PuTTY
Client/Desktop applications / Software for system administration

Vendor: Simon Tatham

Description

The vulnerability allows a remote attacker to perform spoofing attack.

The vulnerability exists due to insufficient verification of data source when processing authentication responses. A remote attacker can send a spoofed authentication prompt even after an SSH session has been established with the original server and trick the victim into providing authentication credentials.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

PuTTY: 0.45 - 0.75

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External links
https://www.chiark.greenend.org.uk/~sgtatham/putty/changes.html
https://git.tartarus.org/?p=simon/putty.git;a=commit;h=1dc5659aa62848f0aeb5de7bd3839fecc7debefa

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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?

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