5.8 - RHSA-2015:1640

Problem Description:

An updated pam package that fixes one security issue is now available for Red Hat Enterprise Linux 6 and 7.

Red Hat Product Security has rated this update as having Moderate security impact. A Common Vulnerability Scoring System (CVSS) base score, which gives a detailed severity rating, is available from the CVE link in the References section.

2. Relevant releases/architectures:

Red Hat Enterprise Linux Client (v. 7) - x86_64 Red Hat Enterprise Linux Client Optional (v. 7) - x86_64 Red Hat Enterprise Linux ComputeNode (v. 7) - x86_64 Red Hat Enterprise Linux ComputeNode Optional (v. 7) - x86_64 Red Hat Enterprise Linux Desktop (v. 6) - i386, x86_64 Red Hat Enterprise Linux Desktop Optional (v. 6) - i386, x86_64 Red Hat Enterprise Linux HPC Node (v. 6) - x86_64 Red Hat Enterprise Linux HPC Node Optional (v. 6) - x86_64 Red Hat Enterprise Linux Server (v. 6) - i386, ppc64, s390x, x86_64 Red Hat Enterprise Linux Server (v. 7) - ppc64, ppc64le, s390x, x86_64 Red Hat Enterprise Linux Workstation (v. 6) - i386, x86_64 Red Hat Enterprise Linux Workstation (v. 7) - x86_64

3. Description:

Pluggable Authentication Modules (PAM) provide a system whereby administrators can set up authentication policies without having to recompile programs to handle authentication.

It was discovered that the _unix_run_helper_binary() function of PAM's unix_pam module could write to a blocking pipe, possibly causing the function to become unresponsive. An attacker able to supply large passwords to the unix_pam module could use this flaw to enumerate valid user accounts, or cause a denial of service on the system. (CVE-2015-3238)

Red Hat would like to thank Sebastien Macke of Trustwave SpiderLabs for reporting this issue.

All pam users are advised to upgrade to this updated package, which contains a backported patch to correct this issue.

4. Solution:

Before applying this update, make sure all previously released errata relevant to your system have been applied.

For details on how to apply this update, refer to:

https://access.redhat.com/articles/11258

5. Bugs fixed (https://bugzilla.redhat.com/):

1228571 - CVE-2015-3238 pam: DoS/user enumeration due to blocking pipe in pam_unix module