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Xen oxenstored Bad Permissions (XSA-353)

high Nessus Plugin ID 149088

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Synopsis

The remote Xen hypervisor installation is missing a security update.

Description

According to its self-reported version number, the Xen hypervisor installed on the remote host is affected by a bad permissions issue. In the Ocaml xenstored implementation, the internal representation of the tree has special cases for the root node, because this node has no parent. Unfortunately, permissions were not checked for certain operations on the root node. Unprivileged guests can get and modify permissions, list, and delete the root node. (Deleting the whole xenstore tree is a host-wide denial of service.) Achieving xenstore write access is also possible. All systems using oxenstored are vulnerable. Building and using oxenstored is the default in the upstream Xen distribution, if the Ocaml compiler is available. Systems using C xenstored are not vulnerable.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

Solution

Apply the appropriate patch according to the vendor advisory.

See Also

https://xenbits.xen.org/xsa/advisory-353.html

Plugin Details

Severity: High

ID: 149088

File Name: xen_server_XSA-353.nasl

Version: 1.2

Type: local

Family: Misc.

Published: 4/29/2021

Updated: 4/30/2021

Configuration: Enable paranoid mode

Supported Sensors: Nessus

Risk Information

VPR

Risk Factor: High

Score: 7.3

CVSS v2

Risk Factor: High

Base Score: 7.2

Temporal Score: 5.3

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

CVSS Score Source: CVE-2020-29479

CVSS v3

Risk Factor: High

Base Score: 8.8

Temporal Score: 7.7

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

Temporal Vector: CVSS:3.0/E:U/RL:O/RC:C

Vulnerability Information

CPE: cpe:/o:xen:xen

Required KB Items: Settings/ParanoidReport, installed_sw/Xen Hypervisor

Exploit Ease: No known exploits are available

Patch Publication Date: 12/15/2020

Vulnerability Publication Date: 12/15/2020

Reference Information

CVE: CVE-2020-29479