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gentooGentoo FoundationGLSA-201703-07
HistoryMar 28, 2017 - 12:00 a.m.

Xen: Privilege Escalation

2017-03-2800:00:00
Gentoo Foundation
security.gentoo.org
33

CVSS2

9

Attack Vector

NETWORK

Attack Complexity

LOW

Authentication

SINGLE

Confidentiality Impact

COMPLETE

Integrity Impact

COMPLETE

Availability Impact

COMPLETE

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

CVSS3

9.9

Attack Vector

NETWORK

Attack Complexity

LOW

Privileges Required

LOW

User Interaction

NONE

Scope

CHANGED

Confidentiality Impact

HIGH

Integrity Impact

HIGH

Availability Impact

HIGH

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

AI Score

8.7

Confidence

High

EPSS

0.001

Percentile

51.0%

Background

Xen is a bare-metal hypervisor.

Description

In CIRRUS_BLTMODE_MEMSYSSRC mode the bitblit copy routine cirrus_bitblt_cputovideo fails to check wethehr the specified memory region is safe.

Impact

A local attacker could potentially execute arbitrary code with privileges of Xen (QEMU) process on the host, gain privileges on the host system, or cause a Denial of Service condition.

Workaround

Running guests in Paravirtualization (PV) mode, or running guests in Hardware-assisted virtualizion (HVM) utilizing stub domains mitigate the issue.

Running HVM guests with the device model in a stubdomain will mitigate the issue.

Changing the video card emulation to stdvga (stdvga=1, vga=”stdvga”, in the xl domain configuration) will avoid the vulnerability.

Resolution

All Xen Tools users should upgrade to the latest version:

 # emerge --sync
 # emerge --ask --oneshot --verbose
 ">=app-emulation/xen-tools-4.7.1-r8"
OSVersionArchitecturePackageVersionFilename
Gentooanyallapp-emulation/xen-tools<Β 4.7.1-r8UNKNOWN

CVSS2

9

Attack Vector

NETWORK

Attack Complexity

LOW

Authentication

SINGLE

Confidentiality Impact

COMPLETE

Integrity Impact

COMPLETE

Availability Impact

COMPLETE

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

CVSS3

9.9

Attack Vector

NETWORK

Attack Complexity

LOW

Privileges Required

LOW

User Interaction

NONE

Scope

CHANGED

Confidentiality Impact

HIGH

Integrity Impact

HIGH

Availability Impact

HIGH

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

AI Score

8.7

Confidence

High

EPSS

0.001

Percentile

51.0%