USN-7051-1: AsyncSSH vulnerability

Releases

• Ubuntu 24.04 LTS
• Ubuntu 22.04 LTS
• Ubuntu 20.04 LTS

Packages

• python-asyncssh - asyncio-based client and server implementation of SSHv2 protocol

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 24.04

• python3-asyncssh - 2.10.1-2ubuntu0.1

Ubuntu 22.04

• python3-asyncssh - 2.5.0-1ubuntu0.1~esm1
  Available with Ubuntu Pro

Ubuntu 20.04

• python3-asyncssh - 1.12.2-1ubuntu0.1

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

References

• CVE-2023-48795

Related notices

• USN-6560-1: openssh-client, ssh-askpass-gnome, openssh, openssh-sftp-server, openssh-server, openssh-tests, ssh
• USN-6561-1: libssh-4, libssh, libssh-gcrypt-dev, libssh-doc, libssh-dev, libssh-gcrypt-4
• USN-6560-2: openssh-client, ssh-askpass-gnome, openssh-client-ssh1, openssh, ssh-krb5, openssh-sftp-server, openssh-server, ssh
• USN-6585-1: libssh2, libssh2-1-dev, libssh2-1
• USN-6589-1: filezilla, filezilla-common
• USN-6598-1: paramiko-doc, paramiko, python3-paramiko
• USN-6738-1: lxd-client, lxd, lxd-tools, lxc2, golang-github-lxc-lxd-dev