PV superpage functionality missing sanity checks

2016-01-2012:00:00

Xen Project

xenbits.xen.org

8.5 High

CVSS3

Attack Vector

NETWORK

Attack Complexity

HIGH

Privileges Required

LOW

User Interaction

NONE

Scope

CHANGED

Confidentiality Impact

HIGH

Integrity Impact

HIGH

Availability Impact

HIGH

CVSS:3.0/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H

6.9 Medium

CVSS2

Access Vector

LOCAL

Access Complexity

MEDIUM

Authentication

NONE

Confidentiality Impact

COMPLETE

Integrity Impact

COMPLETE

Availability Impact

COMPLETE

AV:L/AC:M/Au:N/C:C/I:C/A:C

0.002 Low

EPSS

Percentile

52.4%

JSON

ISSUE DESCRIPTION

The PV superpage functionality lacks certain validity checks on data being passed to the hypervisor by guests. This is the case for the page identifier (MFN) passed to MMUEXT_MARK_SUPER and MMUEXT_UNMARK_SUPER sub-ops of the HYPERVISOR_mmuext_op hypercall as well as for various forms of page table updates.

IMPACT

Use of the feature, which is disabled by default, may have unknown effects, ranging from information leaks through Denial of Service to privilege escalation.

VULNERABLE SYSTEMS

Only systems which enable the PV superpage feature are affected. That is, only systems with an allowsuperpage' setting on the hypervisor command line. Note that in Xen 4.0.x and 3.4.x the option is named allowhugepage’.
Xen versions 3.4.0, 3.4.1, and from 4.1 onwards are affected.
Only x86 systems are affected.
Only PV guests can exploit the vulnerability.