Detections
Analytics

Xen xenstore watch notification Information Disclosure (XSA-115)

low Nessus Plugin ID 144755

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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 an information disclosure vulnerability due to a lack of permission checks for xenstore watch event reporting. A guest administrator can watch the root xenstored node, which will cause notifications for every created, modified, and deleted key. A guest administrator can also use the special watches, which will cause a notification every time a domain is created and destroyed. Data may include: number, type, and domids of other VMs; existence and domids of driver domains;
numbers of virtual interfaces, block devices, vcpus; existence of virtual framebuffers and their backend style (e.g., existence of VNC service); Xen VM UUIDs for other domains; timing information about domain creation and device setup;
and some hints at the backend provisioning of VMs and their devices. The watch events do not contain values stored in xenstore, only key names. A guest administrator can observe non-sensitive domain and device lifecycle events relating to other guests. This information allows some insight into overall system configuration (including the number and general nature of other guests), and configuration of other guests (including the number and general nature of other guests' devices). This information might be commercially interesting or might make other attacks easier. There is not believed to be exposure of sensitive data. Specifically, there is no exposure of VNC passwords, port numbers, pathnames in host and guest filesystems, cryptographic keys, or within-guest data.

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 or workaround according to the vendor advisory.

See Also

https://xenbits.xen.org/xsa/advisory-115.html

Plugin Details

Severity: Low

ID: 144755

File Name: xen_server_XSA-115.nasl

Version: 1.3

Type: local

Family: Misc.

Published: 1/6/2021

Updated: 6/3/2021

Configuration: Enable paranoid mode

Supported Sensors: Nessus

Risk Information

VPR

Risk Factor: Low

Score: 2.2

CVSS v2

Risk Factor: Low

Base Score: 2.1

Temporal Score: 1.6

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

CVSS Score Source: CVE-2020-29480

CVSS v3

Risk Factor: Low

Base Score: 2.3

Temporal Score: 2

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

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-2020-29480

IAVB: 2020-B-0077-S