RHSA-2010:0891 - Security Advisory

Topic

Updated pam packages that fix three security issues are now available for
Red Hat Enterprise Linux 6.

The Red Hat Security Response Team has rated this update as having moderate
security impact. Common Vulnerability Scoring System (CVSS) base scores,
which give detailed severity ratings, are available for each vulnerability
from the CVE links in the References section.

Description

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

It was discovered that the pam_namespace module executed the external
script namespace.init with an unchanged environment inherited from an
application calling PAM. In cases where such an environment was untrusted
(for example, when pam_namespace was configured for setuid applications
such as su or sudo), a local, unprivileged user could possibly use this
flaw to escalate their privileges. (CVE-2010-3853)

It was discovered that the pam_env and pam_mail modules used root
privileges while accessing user's files. A local, unprivileged user could
use this flaw to obtain information, from the lines that have the KEY=VALUE
format expected by pam_env, from an arbitrary file. Also, in certain
configurations, a local, unprivileged user using a service for which the
pam_mail module was configured for, could use this flaw to obtain limited
information about files or directories that they do not have access to.
(CVE-2010-3435)

Note: As part of the fix for CVE-2010-3435, this update changes the default
value of pam_env's configuration option user_readenv to 0, causing the
module to not read user's ~/.pam_environment configuration file by default,
as reading it may introduce unexpected changes to the environment of the
service using PAM, or PAM modules consulted after pam_env.

It was discovered that the pam_xauth module did not verify the return
values of the setuid() and setgid() system calls. A local, unprivileged
user could use this flaw to execute the xauth command with root privileges
and make it read an arbitrary input file. (CVE-2010-3316)

Red Hat would like to thank Sebastian Krahmer of the SuSE Security Team for
reporting the CVE-2010-3435 issue.

All pam users should upgrade to these updated packages, which contain
backported patches to correct these issues.

Solution

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

This update is available via the Red Hat Network. Details on how to
use the Red Hat Network to apply this update are available at
http://kbase.redhat.com/faq/docs/DOC-11259

Affected Products

• Red Hat Enterprise Linux Server 6 x86_64
• Red Hat Enterprise Linux Server 6 i386
• Red Hat Enterprise Linux Server - Extended Life Cycle Support 6 x86_64
• Red Hat Enterprise Linux Server - Extended Life Cycle Support 6 i386
• Red Hat Enterprise Linux Workstation 6 x86_64
• Red Hat Enterprise Linux Workstation 6 i386
• Red Hat Enterprise Linux Desktop 6 x86_64
• Red Hat Enterprise Linux Desktop 6 i386
• Red Hat Enterprise Linux for IBM z Systems 6 s390x
• Red Hat Enterprise Linux for Power, big endian 6 ppc64
• Red Hat Enterprise Linux for Scientific Computing 6 x86_64
• Red Hat Enterprise Linux Server from RHUI 6 x86_64
• Red Hat Enterprise Linux Server from RHUI 6 i386
• Red Hat Enterprise Linux Server - Extended Life Cycle Support (for IBM z Systems) 6 s390x
• Red Hat Enterprise Linux Server - Extended Life Cycle Support Extension 6 x86_64
• Red Hat Enterprise Linux Server - Extended Life Cycle Support Extension 6 i386
• Red Hat Enterprise Linux Server - Extended Life Cycle Support Extension (for IBM z Systems) 6 s390x

Fixes

• BZ - 637898 - CVE-2010-3316 pam: pam_xauth missing return value checks from setuid() and similar calls
• BZ - 641335 - CVE-2010-3435 pam: pam_env and pam_mail accessing users' file with root privileges
• BZ - 643043 - CVE-2010-3853 pam: pam_namespace executes namespace.init with service's environment

CVEs

• CVE-2010-3853
• CVE-2010-3316
• CVE-2010-3435
• CVE-2010-4707
• CVE-2010-4708

References

• http://www.redhat.com/security/updates/classification/#moderate