Debian DSA-4112-1 : xen - security update

Medium Nessus Plugin ID 106820

Synopsis

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

Description

Multiple vulnerabilities have been discovered in the Xen hypervisor :

- CVE-2017-17563 Jan Beulich discovered that an incorrect reference count overflow check in x86 shadow mode may result in denial of service or privilege escalation.

- CVE-2017-17564 Jan Beulich discovered that improper x86 shadow mode reference count error handling may result in denial of service or privilege escalation.

- CVE-2017-17565 Jan Beulich discovered that an incomplete bug check in x86 log-dirty handling may result in denial of service.

- CVE-2017-17566 Jan Beulich discovered that x86 PV guests may gain access to internally used pages which could result in denial of service or potential privilege escalation.

In addition this update ships the 'Comet' shim to address the Meltdown class of vulnerabilities for guests with legacy PV kernels. In addition, the package provides the 'Xen PTI stage 1' mitigation which is built-in and enabled by default on Intel systems, but can be disabled with `xpti=false' on the hypervisor command line (It does not make sense to use both xpti and the Comet shim.)

Please refer to the following URL for more details on how to configure individual mitigation strategies:
https://xenbits.xen.org/xsa/advisory-254.html

Additional information can also be found in README.pti and README.comet.

Solution

Upgrade the xen packages.

For the stable distribution (stretch), these problems have been fixed in version 4.8.3+comet2+shim4.10.0+comet3-1+deb9u4.1.

See Also

https://security-tracker.debian.org/tracker/CVE-2017-17563

https://security-tracker.debian.org/tracker/CVE-2017-17564

https://security-tracker.debian.org/tracker/CVE-2017-17565

https://security-tracker.debian.org/tracker/CVE-2017-17566

https://xenbits.xen.org/xsa/advisory-254.html

https://security-tracker.debian.org/tracker/xen

https://packages.debian.org/source/stretch/xen

http://www.debian.org/security/2018/dsa-4112

Plugin Details

Severity: Medium

ID: 106820

File Name: debian_DSA-4112.nasl

Version: Revision: 3.1

Type: local

Agent: unix

Published: 2018/02/15

Modified: 2018/02/15

Dependencies: 12634

Risk Information

Risk Factor: Medium

CVSSv2

Base Score: 6.9

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

CVSSv3

Base Score: 7.8

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

Vulnerability Information

CPE: p-cpe:/a:debian:debian_linux:xen, cpe:/o:debian:debian_linux:9.0

Required KB Items: Host/local_checks_enabled, Host/Debian/release, Host/Debian/dpkg-l

Patch Publication Date: 2018/02/14

Reference Information

CVE: CVE-2017-17563, CVE-2017-17564, CVE-2017-17565, CVE-2017-17566

DSA: 4112