RHEL 5 : kernel (RHSA-2012:0721)

This script is Copyright (C) 2012-2014 Tenable Network Security, Inc.


Synopsis :

The remote Red Hat host is missing one or more security updates.

Description :

Updated kernel packages that fix two security issues are now available
for Red Hat Enterprise Linux 5.

The Red Hat Security Response Team has rated this update as having
important 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.

The kernel packages contain the Linux kernel, the core of any Linux
operating system.

This update fixes the following security issues :

* It was found that the Xen hypervisor implementation as shipped with
Red Hat Enterprise Linux 5 did not properly restrict the syscall
return addresses in the sysret return path to canonical addresses. An
unprivileged user in a 64-bit para-virtualized guest, that is running
on a 64-bit host that has an Intel CPU, could use this flaw to crash
the host or, potentially, escalate their privileges, allowing them to
execute arbitrary code at the hypervisor level. (CVE-2012-0217,
Important)

* It was found that guests could trigger a bug in earlier AMD CPUs,
leading to a CPU hard lockup, when running on the Xen hypervisor
implementation. An unprivileged user in a 64-bit para-virtualized
guest could use this flaw to crash the host. Warning: After installing
this update, hosts that are using an affected AMD CPU (refer to Red
Hat Bugzilla bug #824966 for a list) will fail to boot. In order to
boot such hosts, the new kernel parameter, allow_unsafe, can be used
('allow_unsafe=on'). This option should only be used with hosts that
are running trusted guests, as setting it to 'on' reintroduces the
flaw (allowing guests to crash the host). (CVE-2012-2934, Moderate)

Note: For Red Hat Enterprise Linux guests, only privileged guest users
can exploit the CVE-2012-0217 and CVE-2012-2934 issues.

Red Hat would like to thank the Xen project for reporting these
issues. Upstream acknowledges Rafal Wojtczuk as the original reporter
of CVE-2012-0217.

Users should upgrade to these updated packages, which contain
backported patches to correct these issues. The system must be
rebooted for this update to take effect.

See also :

https://www.redhat.com/security/data/cve/CVE-2012-0217.html
https://www.redhat.com/security/data/cve/CVE-2012-2934.html
https://bugzilla.redhat.com/show_bug.cgi?id=824966
http://rhn.redhat.com/errata/RHSA-2012-0721.html

Solution :

Update the affected packages.

Risk factor :

High / CVSS Base Score : 7.2
(CVSS2#AV:L/AC:L/Au:N/C:C/I:C/A:C)
CVSS Temporal Score : 6.3
(CVSS2#E:ND/RL:OF/RC:C)
Public Exploit Available : true

Family: Red Hat Local Security Checks

Nessus Plugin ID: 59467 ()

Bugtraq ID: 53961

CVE ID: CVE-2012-0217
CVE-2012-2934