FreeBSD : xen-kernel -- x86: Disallow L3 recursive pagetable for 32-bit PV guests (45ca25b5-ba4d-11e6-ae1b-002590263bf5)

high Nessus Plugin ID 95500

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Synopsis

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

Description

The Xen Project reports :

On real hardware, a 32-bit PAE guest must leave the USER and RW bit clear in L3 pagetable entries, but the pagetable walk behaves as if they were set. (The L3 entries are cached in processor registers, and don't actually form part of the pagewalk.)

When running a 32-bit PV guest on a 64-bit Xen, Xen must always OR in the USER and RW bits for L3 updates for the guest to observe architectural behaviour. This is unsafe in combination with recursive pagetables.

As there is no way to construct an L3 recursive pagetable in native 32-bit PAE mode, disallow this option in 32-bit PV guests.

A malicious 32-bit PV guest administrator can escalate their privilege to that of the host.

Solution

Update the affected package.

Plugin Details

Severity: High

ID: 95500

File Name: freebsd_pkg_45ca25b5ba4d11e6ae1b002590263bf5.nasl

Version: 3.3

Type: local

Family: FreeBSD Local Security Checks

Published: 12/5/2016

Updated: 1/4/2021

Supported Sensors: Nessus

Risk Information

VPR

Risk Factor: Medium

Score: 6.5

CVSS v2

Risk Factor: Medium

Base Score: 6.8

Vector: CVSS2#AV:L/AC:L/Au:S/C:C/I:C/A:C

CVSS v3

Risk Factor: High

Base Score: 8.2

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

Vulnerability Information

CPE: p-cpe:/a:freebsd:freebsd:xen-kernel, cpe:/o:freebsd:freebsd

Required KB Items: Host/local_checks_enabled, Host/FreeBSD/release, Host/FreeBSD/pkg_info

Patch Publication Date: 12/4/2016

Vulnerability Publication Date: 9/8/2016

Reference Information

CVE: CVE-2016-7092

Detections

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