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TITLE:
Xen DR7 and CR4 Register Handling Denial of Service Vulnerabilities

SECUNIA ADVISORY ID:
SA28405

VERIFY ADVISORY:
http://secunia.com/advisories/28405/

CRITICAL:
Not critical

IMPACT:
DoS

WHERE:
Local system

SOFTWARE:
Xen 3.x
http://secunia.com/product/15863/

DESCRIPTION:
Some vulnerabilities have been reported in Xen, which can be
exploited by malicious, local users to cause a DoS (Denial of
Service).

1) An error within the handling of the DR7 debug register can be
exploited out of a guest system to crash the hypervisor by setting
certain breakpoints.

Successful exploitation may require that a HVM hypervisor is used.

2) Access to the CR4 register is not properly checked. This can be
exploited out of a guest system to e.g. crash DomU or Dom0 domains.

Successful exploitation may require that a paravirtualised kernel is
used.

SOLUTION:
Restrict access to trusted users only.

PROVIDED AND/OR DISCOVERED BY:
Reported by Jan Beulich.

ORIGINAL ADVISORY:
http://lists.xensource.com/archives/html/xen-devel/2007-10/msg01048.html
http://lists.xensource.com/archives/html/xen-devel/2007-10/msg00932.html

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About:
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