Pluggable Authentication Modules provide a system whereby administrators can set up authentication policies without having to recompile programs to handle authentication. A stack-based buffer overflow flaw was found in the way the pam_env module parsed users" "~/.pam_environment" files. If an application"s PAM configuration contained "user_readenv=1" , a local attacker could use this flaw to crash the application or, possibly, escalate their privileges. A denial of service flaw was found in the way the pam_env module expanded certain environment variables. If an application"s PAM configuration contained "user_readenv=1" , a local attacker could use this flaw to cause the application to enter an infinite loop. Red Hat would like to thank Kees Cook of the Google ChromeOS Team for reporting the CVE-2011-3148 and CVE-2011-3149 issues. These updated pam packages include numerous bug fixes and enhancements. Space precludes documenting all of these changes in this advisory. Users are directed to the Red Hat Enterprise Linux 6.4 Technical Notes, linked to in the References, for information on the most significant of these changes. All pam users are advised to upgrade to these updated packages, which contain backported patches to correct these issues and add these enhancements.