USN-2710-2: OpenSSH regression

Releases

• Ubuntu 15.04
• Ubuntu 14.04 ESM
• Ubuntu 12.04

Packages

• 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

• openssh-server - 1:6.6p1-2ubuntu2.3

Ubuntu 12.04

• openssh-server - 1:5.9p1-5ubuntu1.7

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

References

• https://launchpad.net/bugs/1485719