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CVE-2020-29566

Published: 15 December 2020

An issue was discovered in Xen through 4.14.x. When they require assistance from the device model, x86 HVM guests must be temporarily de-scheduled. The device model will signal Xen when it has completed its operation, via an event channel, so that the relevant vCPU is rescheduled. If the device model were to signal Xen without having actually completed the operation, the de-schedule / re-schedule cycle would repeat. If, in addition, Xen is resignalled very quickly, the re-schedule may occur before the de-schedule was fully complete, triggering a shortcut. This potentially repeating process uses ordinary recursive function calls, and thus could result in a stack overflow. A malicious or buggy stubdomain serving a HVM guest can cause Xen to crash, resulting in a Denial of Service (DoS) to the entire host. Only x86 systems are affected. Arm systems are not affected. Only x86 stubdomains serving HVM guests can exploit the vulnerability.

Notes

AuthorNote
mdeslaur
hypervisor packages are in universe. For
issues in the hypervisor, add appropriate
tags to each section, ex:
Tags_xen: universe-binary

Priority

Medium

Cvss 3 Severity Score

5.5

Score breakdown

Status

Package Release Status
xen
Launchpad, Ubuntu, Debian
bionic Needed

focal Needed

groovy Ignored
(end of life)
hirsute Ignored
(end of life)
impish Ignored
(end of life)
jammy Not vulnerable
(4.11.4+57-g41a822c392-2)
kinetic Not vulnerable
(4.11.4+57-g41a822c392-2)
lunar Not vulnerable
(4.11.4+57-g41a822c392-2)
mantic Not vulnerable
(4.11.4+57-g41a822c392-2)
trusty Does not exist

upstream Needs triage

xenial Needed

Binaries built from this source package are in Universe and so are supported by the community.

Severity score breakdown

Parameter Value
Base score 5.5
Attack vector Local
Attack complexity Low
Privileges required Low
User interaction None
Scope Unchanged
Confidentiality None
Integrity impact None
Availability impact High
Vector CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H