Xen IRQ Infinite Loop DoS (XSA-356)

medium Nessus Plugin ID 144743

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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 denial of service vulnerability due to an issue when handling IRQ vectors. When moving IRQs between CPUs to distribute the load of IRQ handling, IRQ vectors are dynamically allocated and de-allocated on the relevant CPUs. De-allocation has to happen when certain constraints are met. If these conditions are not met when first checked, the checking CPU may send an interrupt to itself, in the expectation that this IRQ will be delivered only after the condition preventing the cleanup has cleared. For two specific IRQ vectors, this expectation was violated, resulting in a continuous stream of self-interrupts, which renders the CPU effectively unusable. A domain with a passed through PCI device can cause lockup of a physical CPU, resulting in a Denial of Service (DoS) to the entire host. Only x86 systems are vulnerable. Arm systems are not vulnerable. Only guests with physical PCI devices passed through to them can exploit the vulnerability.

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.

Plugin Details

Severity: Medium

ID: 144743

File Name: xen_server_XSA-356.nasl

Version: 1.3

Type: local

Family: Misc.

Published: 1/5/2021

Updated: 6/3/2021

Configuration: Enable paranoid mode

Supported Sensors: Nessus

Risk Information

VPR

Risk Factor: Low

Score: 3.6

CVSS v2

Risk Factor: Medium

Base Score: 4.9

Temporal Score: 3.6

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

CVSS Score Source: CVE-2020-29567

CVSS v3

Risk Factor: Medium

Base Score: 6.2

Temporal Score: 5.4

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

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

Vulnerability Information

CPE: cpe:/o:xen:xen

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

Exploit Ease: No known exploits are available

Patch Publication Date: 12/15/2020

Vulnerability Publication Date: 12/15/2020

Reference Information

CVE: CVE-2020-29567

IAVB: 2020-B-0077-S

Detections

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