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Ubuntu Security Notice USN-2935-2
March 16, 2016

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

– Ubuntu 15.10
– Ubuntu 14.04 LTS
– Ubuntu 12.04 LTS

Summary:

USN-2935-1 introduced a regression in PAM.

Software Description:
– pam: Pluggable Authentication Modules

Details:

USN-2935-1 fixed vulnerabilities in PAM. The updates contained a packaging
change that prevented upgrades in certain multiarch environments. This
update fixes the problem.

We apologize for the inconvenience.

Original advisory details:

It was discovered that the PAM pam_userdb module incorrectly used a
case-insensitive method when comparing hashed passwords. A local attacker
could possibly use this issue to make brute force attacks easier. This
issue only affected Ubuntu 12.04 LTS and Ubuntu 14.04 LTS. (CVE-2013-7041)
Sebastian Krahmer discovered that the PAM pam_timestamp module incorrectly
performed filtering. A local attacker could use this issue to create
arbitrary files, or possibly bypass authentication. This issue only
affected Ubuntu 12.04 LTS and Ubuntu 14.04 LTS. (CVE-2014-2583)
Sebastien Macke discovered that the PAM pam_unix module incorrectly handled
large passwords. A local attacker could possibly use this issue in certain
environments to enumerate usernames or cause a denial of service.
(CVE-2015-3238)

Update instructions:

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

Ubuntu 15.10:
libpam-modules 1.1.8-3.1ubuntu3.2

Ubuntu 14.04 LTS:
libpam-modules 1.1.8-1ubuntu2.2

Ubuntu 12.04 LTS:
libpam-modules 1.1.3-7ubuntu2.2

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

References:
http://www.ubuntu.com/usn/usn-2935-2
http://www.ubuntu.com/usn/usn-2935-1
https://launchpad.net/bugs/1558114

Package Information:
https://launchpad.net/ubuntu/+source/pam/1.1.8-3.1ubuntu3.2
https://launchpad.net/ubuntu/+source/pam/1.1.8-1ubuntu2.2
https://launchpad.net/ubuntu/+source/pam/1.1.3-7ubuntu2.2

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