#VU84537 Inadequate encryption strength in OpenSSH - CVE-2023-48795

Vulnerability identifier: #VU84537

Vulnerability risk: Low

CVSSv4.0: 2.9 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:P/U:Clear]

CVE-ID: CVE-2023-48795

CWE-ID: CWE-326

Exploitation vector: Network

Exploit availability: Yes

Vulnerable software:
OpenSSH
Server applications / Remote management servers, RDP, SSH

Vendor: OpenSSH

Description

The vulnerability allows a remote attacker to perform MitM attack.

The vulnerability exists due to incorrect implementation of the SSH Binary Packet Protocol (BPP), which mishandles the handshake phase and the use of sequence numbers. A remote attacker can perform MitM attack and delete the SSH2_MSG_EXT_INFO message sent before authentication starts, allowing the attacker to disable a subset of the keystroke timing obfuscation features introduced in OpenSSH 9.5.

The vulnerability was dubbed "Terrapin attack" and it affects both client and server implementations.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

OpenSSH: 5.0p1 - 9.5p1

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External links
https://www.openssh.com/openbsd.html
https://github.com/openssh/openssh-portable/commits/master
https://www.openssh.com/txt/release-9.6
https://www.terrapin-attack.com

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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. However, proof of concept for this vulnerability is available.