An OpenSSH regression update has been released for Ubuntu Linux 18.04 LTS.

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Ubuntu Security Notice USN-3809-2
August 12, 2021

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

- Ubuntu 18.04 LTS

Summary:

USN-3809-1 introduced a regression in OpenSSH.

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

Details:

USN-3809-1 fixed vulnerabilities in OpenSSH. The update for CVE-2018-15473
was incomplete and could introduce a regression in certain environments.
This update fixes the problem.

We apologize for the inconvenience.

Original advisory details:

Robert Swiecki discovered that OpenSSH incorrectly handled certain messages.
An attacker could possibly use this issue to cause a denial of service.
This issue only affected Ubuntu 14.04 LTS and Ubuntu 16.04 LTS.
(CVE-2016-10708)
It was discovered that OpenSSH incorrectly handled certain requests.
An attacker could possibly use this issue to access sensitive information.
(CVE-2018-15473)

Update instructions:

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

Ubuntu 18.04 LTS:
openssh-server 1:7.6p1-4ubuntu0.5

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

References:
  https://ubuntu.com/security/notices/USN-3809-2
  https://ubuntu.com/security/notices/USN-3809-1
  https://launchpad.net/bugs/1934501

Package Information:
  https://launchpad.net/ubuntu/+source/openssh/1:7.6p1-4ubuntu0.5