FreeBSD : xen-kernel -- vulnerability in the iret hypercall handler (8c31b288-27ec-11e5-a4a5-002590263bf5)

This script is Copyright (C) 2015 Tenable Network Security, Inc.


Synopsis :

The remote FreeBSD host is missing a security-related update.

Description :

The Xen Project reports :

A buggy loop in Xen's compat_iret() function iterates the wrong way
around a 32-bit index. Any 32-bit PV guest kernel can trigger this
vulnerability by attempting a hypercall_iret with EFLAGS.VM set.

Given the use of __get/put_user(), and that the virtual addresses in
question are contained within the lower canonical half, the guest
cannot clobber any hypervisor data. Instead, Xen will take up to 2^33
pagefaults, in sequence, effectively hanging the host.

Malicious guest administrators can cause a denial of service affecting
the whole system.

See also :

http://xenbits.xen.org/xsa/advisory-136.html
http://www.nessus.org/u?ae4eda3e

Solution :

Update the affected package.

Risk factor :

Medium / CVSS Base Score : 4.9
(CVSS2#AV:L/AC:L/Au:N/C:N/I:N/A:C)

Family: FreeBSD Local Security Checks

Nessus Plugin ID: 84709 ()

Bugtraq ID:

CVE ID: CVE-2015-4164

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