Articles / Ubuntu: New PAM packages fi…

Ubuntu: New PAM packages fix security vulnerabilities

Kees Cook discovered that the PAM pam_env module incorrectly handled certain malformed environment files. A local attacker could use this flaw to cause a denial of service, or possibly gain privileges. The default compiler options for affected releases should reduce the vulnerability to a denial of service. Kees Cook discovered that the PAM pam_env module incorrectly handled variable expansion. A local attacker could use this flaw to cause a denial of service. Stephane Chazelas discovered that the PAM pam_motd module incorrectly cleaned the environment during execution of the motd scripts. In certain environments, a local attacker could use this to execute arbitrary code as root, and gain privileges.

Updated packages are available from security.ubuntu.com.

==========================================================================
Ubuntu Security Notice USN-1237-1
October 24, 2011

pam vulnerabilities
==========================================================================

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

- Ubuntu 11.10
- Ubuntu 11.04
- Ubuntu 10.10
- Ubuntu 10.04 LTS
- Ubuntu 8.04 LTS

Summary:

PAM could be made to crash or run programs as an administrator.

Software Description:
- pam: Pluggable Authentication Modules

Details:

Kees Cook discovered that the PAM pam_env module incorrectly handled
certain malformed environment files. A local attacker could use this flaw
to cause a denial of service, or possibly gain privileges. The default
compiler options for affected releases should reduce the vulnerability to a
denial of service. (CVE-2011-3148)

Kees Cook discovered that the PAM pam_env module incorrectly handled
variable expansion. A local attacker could use this flaw to cause a denial
of service. (CVE-2011-3149)

Stephane Chazelas discovered that the PAM pam_motd module incorrectly
cleaned the environment during execution of the motd scripts. In certain
environments, a local attacker could use this to execute arbitrary code
as root, and gain privileges.

Update instructions:

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

Ubuntu 11.10:
 libpam-modules                  1.1.3-2ubuntu2.1

Ubuntu 11.04:
 libpam-modules                  1.1.2-2ubuntu8.4

Ubuntu 10.10:
 libpam-modules                  1.1.1-4ubuntu2.4

Ubuntu 10.04 LTS:
 libpam-modules                  1.1.1-2ubuntu5.4

Ubuntu 8.04 LTS:
 libpam-modules                  0.99.7.1-5ubuntu6.5

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

References:
 http://www.ubuntu.com/usn/usn-1237-1
 CVE-2011-3148, CVE-2011-3149, CVE-2011-3628

Package Information:
 https://launchpad.net/ubuntu/+source/pam/1.1.3-2ubuntu2.1
 https://launchpad.net/ubuntu/+source/pam/1.1.2-2ubuntu8.4
 https://launchpad.net/ubuntu/+source/pam/1.1.1-4ubuntu2.4
 https://launchpad.net/ubuntu/+source/pam/1.1.1-2ubuntu5.4
 https://launchpad.net/ubuntu/+source/pam/0.99.7.1-5ubuntu6.5
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