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Ubuntu Security Notice USN-7270-2
February 18, 2025

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

- Ubuntu 18.04 LTS
- Ubuntu 16.04 LTS

Summary:

OpenSSH could be made to bypass the server identity check.

Software Description:
- openssh: secure shell (SSH) for secure access to remote machines

Details:

USN-7270-1 fixed a vulnerability in OpenSSH. This update provides
the corresponding update for Ubuntu 16.04 LTS and Ubuntu 18.04 LTS.

Original advisory details:

 It was discovered that the OpenSSH client incorrectly handled the
 non-default VerifyHostKeyDNS option. If that option were enabled, an
 attacker could possibly impersonate a server by completely bypassing the
 server identity check. (CVE-2025-26465)

Update instructions:

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

Ubuntu 18.04 LTS
  openssh-client                  1:7.6p1-4ubuntu0.7+esm4
                                  Available with Ubuntu Pro
  openssh-server                  1:7.6p1-4ubuntu0.7+esm4
                                  Available with Ubuntu Pro

Ubuntu 16.04 LTS
  openssh-client                  1:7.2p2-4ubuntu2.10+esm7
                                  Available with Ubuntu Pro
  openssh-server                  1:7.2p2-4ubuntu2.10+esm7
                                  Available with Ubuntu Pro

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

References:
  https://ubuntu.com/security/notices/USN-7270-2
  https://ubuntu.com/security/notices/USN-7270-1
  CVE-2025-26465