(Red Hat Issues Fix for Linux Kernel) Xen Exception Handling Bugs Let Local Users on a Guest System Cause Denial of Service Conditions on the Host System
SecurityTracker Alert ID: 1034700|
SecurityTracker URL: http://securitytracker.com/id/1034700
(Links to External Site)
Date: Jan 19 2016
Denial of service via network|
Fix Available: Yes Vendor Confirmed: Yes |
Version(s): RHEL 6.2|
Two vulnerabilities were reported in Xen. A local user on the guest system can cause denial of service conditions on the host system. The Linux Kernel is affected.|
The processing of benign exceptions may result in an infinite loop in the CPU. A local user on the guest system can exploit this to cause denial of service conditions on the host system.
An alignment check exception may be triggered by a 32-bit guest [CVE-2015-5307].
A debug exception can be triggered [CVE-2015-8104].
ARM is not affected.
x86 PV VMs are not affected.
x86 CPUs from all manufacturers are affected.
Ben Serebrin from Google and Jan Beulich from SUSE reported these vulnerabilities.
A local user on the guest system can cause denial of service conditions on the host system.|
Red Hat has issued a fix for the Linux Kernel.|
The Red Hat advisory is available at:
Vendor URL: rhn.redhat.com/errata/RHSA-2016-0046.html (Links to External Site)
Exception handling error|
|Underlying OS: Linux (Red Hat Enterprise)|
This archive entry is a follow-up to the message listed below.|
Source Message Contents
Subject: [RHSA-2016:0046-01] Important: kernel security update|
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Red Hat Security Advisory
Synopsis: Important: kernel security update
Advisory ID: RHSA-2016:0046-01
Product: Red Hat Enterprise Linux
Advisory URL: https://rhn.redhat.com/errata/RHSA-2016-0046.html
Issue date: 2016-01-19
CVE Names: CVE-2015-5307 CVE-2015-8104
Updated kernel packages that fix two security issues are now available for
Red Hat Enterprise Linux 6.2 Advanced Update Support.
Red Hat Product Security 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.
2. Relevant releases/architectures:
Red Hat Enterprise Linux AUS (v. 6.2 server) - noarch, x86_64
Red Hat Enterprise Linux Server Optional AUS (v. 6.2) - x86_64
The kernel packages contain the Linux kernel, the core of any Linux
* It was found that the x86 ISA (Instruction Set Architecture) is prone to
a denial of service attack inside a virtualized environment in the form of
an infinite loop in the microcode due to the way (sequential) delivering of
benign exceptions such as #AC (alignment check exception) and #DB (debug
exception) is handled. A privileged user inside a guest could use these
flaws to create denial of service conditions on the host kernel.
(CVE-2015-5307, CVE-2015-8104, Important)
Red Hat would like to thank Ben Serebrin of Google Inc. for reporting the
All kernel users are advised to upgrade to these updated packages, which
contain backported patches to correct these issues. The system must be
rebooted for this update to take effect.
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:
5. Bugs fixed (https://bugzilla.redhat.com/):
1277172 - CVE-2015-5307 virt: guest to host DoS by triggering an infinite loop in microcode via #AC exception
1278496 - CVE-2015-8104 virt: guest to host DoS by triggering an infinite loop in microcode via #DB exception
6. Package List:
Red Hat Enterprise Linux AUS (v. 6.2 server):
Red Hat Enterprise Linux Server Optional AUS (v. 6.2):
These packages are GPG signed by Red Hat for security. Our key and
details on how to verify the signature are available from
The Red Hat security contact is <firstname.lastname@example.org>. More contact
details at https://access.redhat.com/security/team/contact/
Copyright 2016 Red Hat, Inc.
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