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AUSCERT External Security Bulletin Redistribution
ESB-2014.0910
Xen Security Advisory CVE-2014-3969 / XSA-98 version 3
10 June 2014
===========================================================================
AusCERT Security Bulletin Summary
---------------------------------
Product: Xen
Publisher: Xen
Operating System: UNIX variants (UNIX, Linux, OSX)
Xen
Impact/Access: Execute Arbitrary Code/Commands -- Existing Account
Resolution: Patch/Upgrade
CVE Names: CVE-2014-3969
Original Bulletin:
http://xenbits.xen.org/xsa/advisory-98.html
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Xen Security Advisory CVE-2014-3969 / XSA-98
version 3
insufficient permissions checks accessing guest memory on ARM
UPDATES IN VERSION 3
====================
CVE assigned.
ISSUE DESCRIPTION
=================
When accessing guest memory Xen does not correctly perform permissions
checks on the (possibly guest provided) virtual address: it only
checks that the mapping is readable by the guest, even when writing on
behalf of the guest. This allows a guest to write to memory which
it should only be able to read.
A guest running on a vulnerable system is able to write to memory
which should be read-only. This includes supposedly read only foreign
mappings established using the grant table mechanism. Such read-only
mappings are commonly used as part of the paravirtualised I/O drivers
(such as guest disk write and network transmit).
In order to exploit this vulnerability the guest must have a mapping
of the memory; it does not allow access to arbitrary addresses.
In the event that a guest executes code from a page which has been
shared read-only with another guest it would be possible to mount a
take over attack on that guest.
IMPACT
======
A domain which is deliberately exchanging data with another,
malicious, domain, may be vulnerable to privilege escalation. The
vulnerability depends on the precise behaviour of the victim domain.
In a typical configuration this means that, depending on the behaviour
of the toolstack or device driver domain, a malicious guest
administrator might be able to escalate their privilege to that of the
whole host.
VULNERABLE SYSTEMS
==================
Both 32- and 64-bit ARM systems are vulnerable from Xen 4.4 onward.
MITIGATION
==========
None.
CREDITS
=======
This issue was discovered by Julien Grall.
RESOLUTION
==========
Applying the appropriate pair of attached patches resolves this issue.
xsa98-unstable-{01,02}.patch xen-unstable
xsa98-4.4-{01,02}.patch Xen 4.4.x
$ sha256sum xsa98*.patch
6f63bc2e0a0a39bbd9137513a5d130ae2c78d1fd2ebf9172bf49456f73f0a67b xsa98-4.4-01.patch
b338472ecce3c31a55d1a936eebbd4e46cb3ad989b91a64d4b8c5d3ca80d875d xsa98-4.4-02.patch
b8535aad5ae969675d59781a81ce0b24491f1abc01aaf36c3620fd7fb6cc84eb xsa98-unstable-01.patch
f5e8a93525a8905653da6377097f77681ff8121b973063ff6081e27547ceaa67 xsa98-unstable-02.patch
$
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