Ubuntu update for openssh

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 openssh to the latest version.

Vulnerable software versions

Ubuntu: 16.04 - 18.04

openssh-client (Ubuntu package): before Ubuntu Pro

openssh-server (Ubuntu package): before Ubuntu Pro (Infra-only)

CPE2.3

• cpe:2.3:o:canonical:ubuntu:16.04:*:*:*:*:*:*:
• cpe:2.3:o:canonical:ubuntu:18.04:*:*:*:*:*:*:
• cpe:2.3:o:canonical:openssh-client_ubuntu_package:*:*:*:*:*:ubuntu:*:
• cpe:2.3:o:canonical:openssh-server_ubuntu_package:*:*:*:*:*:ubuntu:*:

External links

http://ubuntu.com/security/notices/USN-6560-2

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.

2) OS Command Injection

EUVDB-ID: #VU84789

Risk: Medium

CVSSv3.1: 6.7 [CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H/E:P/RL:O/RC:C]

CVE-ID: CVE-2023-51385

CWE-ID: CWE-78 - Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')

Exploit availability: Yes

Description

The vulnerability allows a remote attacker to execute arbitrary shell commands on the target system.

The vulnerability exists due to improper input validation when processing user names, if a user name or host name has shell metacharacters, and this name is referenced by an expansion token in certain situations. A remote attacker can execute arbitrary OS commands via an untrusted Git repository.

Mitigation

Update the affected package openssh to the latest version.

Vulnerable software versions

Ubuntu: 16.04 - 18.04

openssh-client (Ubuntu package): before Ubuntu Pro

openssh-server (Ubuntu package): before Ubuntu Pro (Infra-only)

CPE2.3

• cpe:2.3:o:canonical:ubuntu:16.04:*:*:*:*:*:*:
• cpe:2.3:o:canonical:ubuntu:18.04:*:*:*:*:*:*:
• cpe:2.3:o:canonical:openssh-client_ubuntu_package:*:*:*:*:*:ubuntu:*:
• cpe:2.3:o:canonical:openssh-server_ubuntu_package:*:*:*:*:*:ubuntu:*:

External links

http://ubuntu.com/security/notices/USN-6560-2

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.