[USN-6561-1] libssh vulnerability

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==========================================================================
Ubuntu Security Notice USN-6561-1
December 19, 2023

libssh vulnerability
==========================================================================

A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 23.10
- Ubuntu 23.04
- Ubuntu 22.04 LTS
- Ubuntu 20.04 LTS

Summary:

A security issue was fixed in libssh.

Software Description:
- libssh: A tiny C SSH library

Details:

Fabian Bäumer, Marcus Brinkmann, Jörg Schwenk discovered that the SSH
protocol was vulnerable to a prefix truncation attack. If a remote attacker
was able to intercept SSH communications, extension negotiation messages
could be truncated, possibly leading to certain algorithms and features
being downgraded. This issue is known as the Terrapin attack. This update
adds protocol extensions to mitigate this issue.

Update instructions:

The problem can be corrected by updating your system to the following
package versions:

Ubuntu 23.10:
libssh-4 0.10.5-3ubuntu1.1

Ubuntu 23.04:
libssh-4 0.10.4-2ubuntu0.2

Ubuntu 22.04 LTS:
libssh-4 0.9.6-2ubuntu0.22.04.2

Ubuntu 20.04 LTS:
libssh-4 0.9.3-2ubuntu2.4

In general, a standard system update will make all the necessary changes.

References:
https://ubuntu.com/security/notices/USN-6561-1
CVE-2023-48795

Package Information:
https://launchpad.net/ubuntu/+source/libssh/0.10.5-3ubuntu1.1
https://launchpad.net/ubuntu/+source/libssh/0.10.4-2ubuntu0.2
https://launchpad.net/ubuntu/+source/libssh/0.9.6-2ubuntu0.22.04.2
https://launchpad.net/ubuntu/+source/libssh/0.9.3-2ubuntu2.4