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FreeBSD : xen-kernel -- vulnerability in the iret hypercall handler (8c31b288-27ec-11e5-a4a5-002590263bf5)

medium Nessus Plugin ID 84709

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Synopsis

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

Description

The Xen Project reports :

A buggy loop in Xen's compat_iret() function iterates the wrong way around a 32-bit index. Any 32-bit PV guest kernel can trigger this vulnerability by attempting a hypercall_iret with EFLAGS.VM set.

Given the use of __get/put_user(), and that the virtual addresses in question are contained within the lower canonical half, the guest cannot clobber any hypervisor data. Instead, Xen will take up to 2^33 pagefaults, in sequence, effectively hanging the host.

Malicious guest administrators can cause a denial of service affecting the whole system.

Solution

Update the affected package.

See Also

http://xenbits.xen.org/xsa/advisory-136.html

http://www.nessus.org/u?8911262e

Plugin Details

Severity: Medium

ID: 84709

File Name: freebsd_pkg_8c31b28827ec11e5a4a5002590263bf5.nasl

Version: 2.4

Type: local

Published: 7/14/2015

Updated: 1/6/2021

Supported Sensors: Nessus

Risk Information

VPR

Risk Factor: Medium

Score: 4.4

CVSS v2

Risk Factor: Medium

Base Score: 4.9

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

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: 7/11/2015

Vulnerability Publication Date: 6/11/2015

Reference Information

CVE: CVE-2015-4164