CVE-2019-18420

Severity CVSS v4.0:

Pending analysis

Type:

CWE-134 Format String Vulnerability

Publication date:

31/10/2019

Last modified:

07/11/2023

Description

An issue was discovered in Xen through 4.12.x allowing x86 PV guest OS users to cause a denial of service via a VCPUOP_initialise hypercall. hypercall_create_continuation() is a variadic function which uses a printf-like format string to interpret its parameters. Error handling for a bad format character was done using BUG(), which crashes Xen. One path, via the VCPUOP_initialise hypercall, has a bad format character. The BUG() can be hit if VCPUOP_initialise executes for a sufficiently long period of time for a continuation to be created. Malicious guests may cause a hypervisor crash, resulting in a Denial of Service (DoS). Xen versions 4.6 and newer are vulnerable. Xen versions 4.5 and earlier are not vulnerable. Only x86 PV guests can exploit the vulnerability. HVM and PVH guests, and guests on ARM systems, cannot exploit the vulnerability.

Impact

Vector 3.x

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H CVSS v3.1 Severity and Metrics:

Base Score: 6.50 MEDIUM
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Attack Vector (AV): Network
Attack Complexity (AC): Low
Privileges Required (PR): Low
User Interaction (UI): None
Scope (S): Unchanged
Confidentiality (C): None
Integrity (I): None
Availability (A): High

Base Score 3.x

6.50

Severity 3.x

MEDIUM

Vector 2.0

AV:N/AC:M/Au:S/C:N/I:N/A:C CVSS v2.0 Severity and Metrics:

Base Score: 6.30 MEDIUM
Vector: AV:N/AC:M/Au:S/C:N/I:N/A:C

Attack Vector (AV): Network
Attack Complexity (AC): Medium
Authentication (Au): Single
Confidentiality (C): None
Integrity (I): None
Availability (A): Complete

Base Score 2.0

6.30

Severity 2.0

MEDIUM

Vulnerable products and versions

CPE	From	Up to
cpe:2.3:o:xen:xen:::::::x86:*		4.12.1 (including)
cpe:2.3:o:debian:debian_linux:9.0:::::::*
cpe:2.3:o:debian:debian_linux:10.0:::::::*
cpe:2.3:o:fedoraproject:fedora:29:::::::*
cpe:2.3:o:fedoraproject:fedora:30:::::::*
cpe:2.3:o:fedoraproject:fedora:31:::::::*

To consult the complete list of CPE names with products and versions, see this page

CPE	From	Up to
cpe:2.3:o:xen:xen:::::::x86:*		4.12.1 (including)
cpe:2.3:o:debian:debian_linux:9.0:::::::*
cpe:2.3:o:debian:debian_linux:10.0:::::::*
cpe:2.3:o:fedoraproject:fedora:29:::::::*
cpe:2.3:o:fedoraproject:fedora:30:::::::*
cpe:2.3:o:fedoraproject:fedora:31:::::::*

CVE-2019-18420

Description

Impact

Vulnerable products and versions

References to Advisories, Solutions, and Tools