[USN-6561-1] libssh vulnerability

Marc Deslauriers marc.deslauriers at canonical.com
Tue Dec 19 15:11:01 UTC 2023

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


A security issue was fixed in libssh.

Software Description:
- libssh: A tiny C SSH library


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.


Package Information:

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