Xen Scrubbed Pages Cache Information Disclosure (XSA-364)

medium Nessus Plugin ID 146596

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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. On Arm, a guest is allowed to control whether memory access bypass the cache. This means that Xen needs to ensure that all writes (such as the ones during scrubbing) have reached memory before handing over the page to a guest. Unfortunately the operation to clean the cache happens before checking if the page was scrubbed. Therefore there is no guarantee when all the writes will reach the memory. A malicious guest may be able to read sensitive data from memory that previously belonged to another guest.

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.

Plugin Details

Severity: Medium

ID: 146596

File Name: xen_server_XSA-364.nasl

Version: 1.4

Type: local

Family: Misc.

Published: 2/19/2021

Updated: 1/26/2022

Configuration: Enable paranoid mode

Supported Sensors: Nessus

Risk Information

VPR

Risk Factor: Low

Score: 3.6

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-2021-26933

CVSS v3

Risk Factor: Medium

Base Score: 5.5

Temporal Score: 4.8

Vector: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/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: 2/16/2021

Vulnerability Publication Date: 2/16/2021

Reference Information

CVE: CVE-2021-26933

IAVB: 2021-B-0011-S

Detections

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