Several local vulnerabilities have been discovered in the Xen hypervisor packages which may lead to the execution of arbitrary code.
The Common Vulnerabilities and Exposures project identifies the following problems :

  - CVE-2007-4993     By use of a specially crafted grub configuration file a     domU user may be able to execute arbitrary code upon the     dom0 when pygrub is being used.

  - CVE-2007-1320     Multiple heap-based buffer overflows in the Cirrus VGA     extension, provided by QEMU, may allow local users to     execute arbitrary code via 'bitblt' heap overflow.

Fixes a security flaw in pygrub handling of config files and a denial-of-service case in ne2k NIC for QEMU.

Fixes the case of disappearing network cards in fully-virtualized guests. NB, it only fixes it for guests created after this errata is installed & XenD restarted. Any pre-existing guests may continue to have problems. To fix existing guests, first ensure XenD has been restarted (service xend restart), then use virt-manager/virsh to remove the network card, and then add it back. This will correct the configuration stored in XenD permanently.

Note that Tenable Network Security has extracted the preceding description block directly from the Fedora security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.

An updated Xen package to fix multiple security issues is now available for Red Hat Enterprise Linux 5.

This update has been rated as having important security impact by the Red Hat Security Response Team.

The Xen package contains the tools for managing the virtual machine monitor in Red Hat Enterprise Linux virtualization.

The following security flaws are fixed in the updated Xen package :

Joris van Rantwijk found a flaw in the Pygrub utility which is used as a boot loader for guest domains. A malicious local administrator of a guest domain could create a carefully crafted grub.conf file which would trigger the execution of arbitrary code outside of that domain.
(CVE-2007-4993)

Tavis Ormandy discovered a heap overflow flaw during video-to-video copy operations in the Cirrus VGA extension code used in Xen. A malicious local administrator of a guest domain could potentially trigger this flaw and execute arbitrary code outside of the domain.
(CVE-2007-1320)

Tavis Ormandy discovered insufficient input validation leading to a heap overflow in the Xen NE2000 network driver. If the driver is in use, a malicious local administrator of a guest domain could potentially trigger this flaw and execute arbitrary code outside of the domain. Xen does not use this driver by default. (CVE-2007-1321)

Users of Xen should update to these erratum packages containing backported patches which correct these issues.

Tavis Ormandy discovered a heap overflow flaw during video-to-video copy operations in the Cirrus VGA extension code that is used in Xen.
A malicious local administrator of a guest domain could potentially trigger this flaw and execute arbitrary code outside of the domain (CVE-2007-1320).

Tavis Ormandy also discovered insufficient input validation leading to a heap overflow in the NE2000 network driver in Xen. If the driver is in use, a malicious local administrator of a guest domain could potentially trigger this flaw and execute arbitrary code outside of the domain (CVE-2007-1321, CVE-2007-5729, CVE-2007-5730).

Steve Kemp found that xen-utils used insecure temporary files within the xenmon tool that could allow local users to truncate arbitrary files (CVE-2007-3919).

Joris van Rantwijk discovered a flaw in Pygrub, which is used as a boot loader for guest domains. A malicious local administrator of a guest domain could create a carefully-crafted grub.conf file which could trigger the execution of arbitrary code outside of that domain (CVE-2007-4993).

Updated packages have been patched to prevent these issues.

Fixes a security flaw in pygrub handling of config files and a denial-of-service case in ne2k NIC for QEMU.

Note that Tenable Network Security has extracted the preceding description block directly from the Fedora security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.

Joris van Rantwijk discovered that the Xen host did not correctly validate the contents of a Xen guests's grug.conf file. Xen guest root users could exploit this to run arbitrary commands on the host when the guest system was rebooted.

Note that Tenable Network Security has extracted the preceding description block directly from the Ubuntu security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.

Detail :

Joris van Rantwijk found a flaw in the Pygrub utility which is used as a boot loader for guest domains. A malicious local administrator of a guest domain could create a carefully crafted grub.conf file which would trigger the execution of arbitrary code outside of that domain.
(CVE-2007-4993)

Tavis Ormandy discovered a heap overflow flaw during video-to-video copy operations in the Cirrus VGA extension code used in Xen. A malicious local administrator of a guest domain could potentially trigger this flaw and execute arbitrary code outside of the domain.
(CVE-2007-1320)

Tavis Ormandy discovered insufficient input validation leading to a heap overflow in the Xen NE2000 network driver. If the driver is in use, a malicious local administrator of a guest domain could potentially trigger this flaw and execute arbitrary code outside of the domain. Xen does not use this driver by default. (CVE-2007-1321)

The remote Oracle Linux 5 host has packages installed that are affected by multiple vulnerabilities as referenced in the ELSA-2007-0323 advisory.

    [3.0.3-25.0.4.el5]
     - QEmu cirrus bitblit bounds check - CVE-2007-1320 (rhbz #296271)
     - QEmu NE2000 overflow check - CVE-2007-1321 (rhbz #296271)
     - Pygrub guest escape - CVE-2007-4993 (rhbz #302821)

Tenable has extracted the preceding description block directly from the Oracle Linux security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

- Fri Oct 26 2007 Daniel P. Berrange <berrange at     redhat.com> - 3.1.0-8.fc7

    - Fixed xenbaked tmpfile flaw (CVE-2007-3919)

    - Wed Sep 26 2007 Daniel P. Berrange <berrange at       redhat.com> - 3.1.0-7.fc7

    - Fixed rtl8139 checksum calculation for Vista (rhbz       #308201)

    - Wed Sep 26 2007 Chris Lalancette <clalance at       redhat.com> - 3.1.0-6.fc7

    - QEmu NE2000 overflow check - CVE-2007-1321

    - Pygrub guest escape - CVE-2007-4993

    - Mon Sep 24 2007 Daniel P. Berrange <berrange at       redhat.com> - 3.1.0-5.fc7

    - Fix generation of manual pages (rhbz #250791)

    - Fix 32-on-64 PVFB for FC6 legacy guests

    - Mon Sep 24 2007 Daniel P. Berrange <berrange at       redhat.com> - 3.1.0-4.fc7

    - Fix VMX assist IRQ handling (rhbz #279581)

    - Sun Sep 23 2007 Daniel P. Berrange <berrange at       redhat.com> - 3.1.0-3.fc7

    - Don't clobber the VIF type attribute in FV guests       (rhbz #247122)

    - Wed Aug 1 2007 Markus Armbruster <armbru at       redhat.com>

    - Put guest's native protocol ABI into xenstore, to       provide for older kernels running 32-on-64.

  - VNC keymap fixes

    - Fix race conditions in LibVNCServer on client       disconnect

    - Mon Jun 11 2007 Daniel P. Berrange <berrange at       redhat.com> - 3.1.0-2.fc7

    - Remove patch which kills VNC monitor

    - Fix HVM save/restore file path to be /var/lib/xen       instead of /tmp

    - Don't spawn a bogus xen-vncfb daemon for HVM guests

    - Fri May 25 2007 Daniel P. Berrange <berrange at       redhat.com> - 3.1.0-1.fc7

    - Updated to official 3.1.0 tar.gz

    - Fixed data corruption from VNC client disconnect (bz       241303)

    - Thu May 17 2007 Daniel P. Berrange <berrange at       redhat.com> - 3.1.0-0.rc7.2.fc7

    - Ensure xen-vncfb processes are cleanedup if guest       quits (bz 240406)

    - Tear down guest if device hotplug fails

Note that Tenable Network Security has extracted the preceding description block directly from the Fedora security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.

ID	Name	Product	Family	Published	Updated	Severity
26931	Debian DSA-1384-1 : xen-utils - several vulnerabilities	Nessus	Debian Local Security Checks	10/9/2007	1/4/2021	high
27763	Fedora 7 : xen-3.1.0-6.fc7 (2007-2270)	Nessus	Fedora Local Security Checks	11/6/2007	1/11/2021	medium
26903	RHEL 5 : xen (RHSA-2007:0323)	Nessus	Red Hat Local Security Checks	10/3/2007	1/14/2021	high
27614	Mandrake Linux Security Advisory : xen (MDKSA-2007:203)	Nessus	Mandriva Local Security Checks	11/2/2007	1/6/2021	high
26933	Fedora Core 6 : xen-3.0.3-12.fc6 (2007-713)	Nessus	Fedora Local Security Checks	10/9/2007	1/11/2021	high
28132	Ubuntu 7.04 : xen-3.0 vulnerability (USN-527-1)	Nessus	Ubuntu Local Security Checks	11/10/2007	1/19/2021	medium
43639	CentOS 5 : xen (CESA-2007:0323)	Nessus	CentOS Local Security Checks	1/6/2010	1/4/2021	high
60261	Scientific Linux Security Update : xen on SL5.x i386/x86_64	Nessus	Scientific Linux Local Security Checks	8/1/2012	1/14/2021	high
67486	Oracle Linux 5 : Important: / xen (ELSA-2007-0323)	Nessus	Oracle Linux Local Security Checks	7/12/2013	10/22/2024	high
27794	Fedora 7 : xen-3.1.0-8.fc7 (2007-2708)	Nessus	Fedora Local Security Checks	11/6/2007	1/11/2021	medium

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