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xenXen ProjectXSA-120
HistoryMar 10, 2015 - 12:00 p.m.

Non-maskable interrupts triggerable by guests

2015-03-1012:00:00
Xen Project
xenbits.xen.org
58

4.9 Medium

CVSS2

Attack Vector

LOCAL

Attack Complexity

LOW

Authentication

NONE

Confidentiality Impact

NONE

Integrity Impact

NONE

Availability Impact

COMPLETE

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

6.5 Medium

CVSS3

Attack Vector

LOCAL

Attack Complexity

LOW

Privileges Required

LOW

User Interaction

NONE

Scope

CHANGED

Confidentiality Impact

HIGH

Integrity Impact

NONE

Availability Impact

NONE

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

7.2 High

AI Score

Confidence

High

0.001 Low

EPSS

Percentile

28.2%

ISSUE DESCRIPTION

Guests are currently permitted to modify all of the (writable) bits in the PCI command register of devices passed through to them. This in particular allows them to disable memory and I/O decoding on the device unless the device is an SR-IOV virtual function, in which case subsequent accesses to the respective MMIO or I/O port ranges would

  • on PCI Express devices - lead to Unsupported Request responses. The treatment of such errors is platform specific. (CVE-2015-2150)
    (Also, the patches in XSA-120 v4 and earlier were incomplete. This incompleteness is CVE-2015-8553. Additional patches are supplied in XSA-120 v5 and later to resolve this issue.)

IMPACT

In the event that the platform surfaces aforementioned UR responses as Non-Maskable Interrupts, and either the OS is configured to treat NMIs as fatal or (e.g. via ACPI’s APEI) the platform tells the OS to treat these errors as fatal, the host would crash, leading to a Denial of Service.

VULNERABLE SYSTEMS

Xen versions 3.3 and onwards are vulnerable due to supporting PCI pass-through. Upstream Linux versions 3.1 and onwards are vulnerable due to supporting PCI backend functionality. Other Linux versions as well as other OS versions may be vulnerable too.
Any domain which is given access to a non-SR-IOV virtual function PCI Express device can take advantage of this vulnerability.

CPENameOperatorVersion
xenge3.3

4.9 Medium

CVSS2

Attack Vector

LOCAL

Attack Complexity

LOW

Authentication

NONE

Confidentiality Impact

NONE

Integrity Impact

NONE

Availability Impact

COMPLETE

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

6.5 Medium

CVSS3

Attack Vector

LOCAL

Attack Complexity

LOW

Privileges Required

LOW

User Interaction

NONE

Scope

CHANGED

Confidentiality Impact

HIGH

Integrity Impact

NONE

Availability Impact

NONE

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

7.2 High

AI Score

Confidence

High

0.001 Low

EPSS

Percentile

28.2%