CVE-2020-29566 Information

Description

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.

CVSS Vector

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Reference

https://xenbits.xenproject.org/xsa/advisory-348.html https://www.debian.org/security/2020/dsa-4812 https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/OBLV6L6Q24PPQ2CRFXDX4Q76KU776GKI/ https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/2C6M6S3CIMEBACH6O7V4H2VDANMO6TVA/ https://security.gentoo.org/glsa/202107-30

Attack Complexity

LOW

Privileges Required

LOW

User Interaction Required

LOW

Scope

NONE

Confidentiality Impact

UNCHANGED

Integrity Impact

NONE

Availability Impact

NONE

Base Score

HIGH

Base Severity

5.5