USN-2710-2: OpenSSH regression

18 August 2015

openssh regression

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

  • Ubuntu 15.04
  • Ubuntu 14.04 LTS
  • Ubuntu 12.04 LTS

Summary

USN-2710-1 introduced a regression in OpenSSH.

Software Description

  • openssh - secure shell (SSH) for secure access to remote machines

Details

USN-2710-1 fixed vulnerabilities in OpenSSH. The upstream fix for CVE-2015-5600 caused a regression resulting in random authentication failures in non-default configurations. This update fixes the problem.

Original advisory details:

Moritz Jodeit discovered that OpenSSH incorrectly handled usernames when using PAM authentication. If an additional vulnerability were discovered in the OpenSSH unprivileged child process, this issue could allow a remote attacker to perform user impersonation. (CVE number pending)

Moritz Jodeit discovered that OpenSSH incorrectly handled context memory when using PAM authentication. If an additional vulnerability were discovered in the OpenSSH unprivileged child process, this issue could allow a remote attacker to bypass authentication or possibly execute arbitrary code. (CVE number pending)

Jann Horn discovered that OpenSSH incorrectly handled time windows for X connections. A remote attacker could use this issue to bypass certain access restrictions. (CVE-2015-5352)

It was discovered that OpenSSH incorrectly handled keyboard-interactive authentication. In a non-default configuration, a remote attacker could possibly use this issue to perform a brute-force password attack. (CVE-2015-5600)

Update instructions

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

Ubuntu 15.04
openssh-server - 1:6.7p1-5ubuntu1.3
Ubuntu 14.04 LTS
openssh-server - 1:6.6p1-2ubuntu2.3
Ubuntu 12.04 LTS
openssh-server - 1:5.9p1-5ubuntu1.7

To update your system, please follow these instructions: https://wiki.ubuntu.com/Security/Upgrades.

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

References