Ubuntu update for libssh

1) Inadequate encryption strength

EUVDB-ID: #VU84537

Risk: Low

CVSSv3.1: 3.2 [CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N/E:U/RL:O/RC:C]

CVE-ID: CVE-2023-48795

CWE-ID: CWE-326 - Inadequate Encryption Strength

Exploit availability: No

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

Update the affected package libssh to the latest version.

Vulnerable software versions

Ubuntu: 20.04 - 23.10

libssh-4 (Ubuntu package): before 0.9.3-2ubuntu2.4

CPE2.3

• cpe:2.3:o:canonical:ubuntu:20.04:*:*:*:*:*:*:
• cpe:2.3:o:canonical:ubuntu:22.04:*:*:*:*:*:*:
• cpe:2.3:o:canonical:ubuntu:23.04:*:*:*:*:*:*:
• cpe:2.3:o:canonical:ubuntu:23.10:*:*:*:*:*:*:
• cpe:2.3:o:canonical:libssh-4_ubuntu_package:*:*:*:*:*:ubuntu:*:

External links

http://ubuntu.com/security/notices/USN-6561-1

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.