Vulnerability CVE-2021-20196

Vulnerability Name:

CVE-2021-20196 (CCN-195793)

Assigned:

2020-12-17

Published:

2021-01-23

Updated:

2023-02-12

Summary:

A NULL pointer dereference flaw was found in the floppy disk emulator of QEMU. This issue occurs while processing read/write ioport commands if the selected floppy drive is not initialized with a block device. This flaw allows a privileged guest user to crash the QEMU process on the host, resulting in a denial of service. The highest threat from this vulnerability is to system availability.

CVSS v3 Severity:

6.5 Medium (CVSS v3.1 Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H)
5.7 Medium (Temporal CVSS v3.1 Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H/E:U/RL:O/RC:C)

Exploitability Metrics:	Attack Vector (AV): Local Attack Complexity (AC): Low Privileges Required (PR): Low User Interaction (UI): None
Scope:	Scope (S): Changed
Impact Metrics:	Confidentiality (C): None Integrity (I): None Availibility (A): High

6.5 Medium (CCN CVSS v3.1 Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H)
5.7 Medium (CCN Temporal CVSS v3.1 Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H/E:U/RL:O/RC:C)

Exploitability Metrics:	Attack Vector (AV): Local Attack Complexity (AC): Low Privileges Required (PR): Low User Interaction (UI): None
Scope:	Scope (S): Changed
Impact Metrics:	Confidentiality (C): None Integrity (I): None Availibility (A): High

3.2 Low (REDHAT CVSS v3.1 Vector: CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:N/I:N/A:L)
2.8 Low (REDHAT Temporal CVSS v3.1 Vector: CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:N/I:N/A:L/E:U/RL:O/RC:C)

Exploitability Metrics:	Attack Vector (AV): Local Attack Complexity (AC): Low Privileges Required (PR): High User Interaction (UI): None
Scope:	Scope (S): Changed
Impact Metrics:	Confidentiality (C): None Integrity (I): None Availibility (A): Low

CVSS v2 Severity:

2.1 Low (CVSS v2 Vector: AV:L/AC:L/Au:N/C:N/I:N/A:P)

Exploitability Metrics:	Access Vector (AV): Local Access Complexity (AC): Low Authentication (Au): None
Impact Metrics:	Confidentiality (C): None Integrity (I): None Availibility (A): Partial

4.6 Medium (CCN CVSS v2 Vector: AV:L/AC:L/Au:S/C:N/I:N/A:C)

Exploitability Metrics:	Access Vector (AV): Local Access Complexity (AC): Low Athentication (Au): Single_Instance
Impact Metrics:	Confidentiality (C): None Integrity (I): None Availibility (A): Complete

Vulnerability Type:

CWE-476

Vulnerability Consequences:

Denial of Service

References:

Source: MITRE
Type: CNA
CVE-2021-20196

Source: secalert@redhat.com
Type: Exploit, Patch, Third Party Advisory
secalert@redhat.com

Source: XF
Type: UNKNOWN
qemu-cve202120196-dos(195793)

Source: secalert@redhat.com
Type: Mailing List, Third Party Advisory
secalert@redhat.com

Source: secalert@redhat.com
Type: Mailing List, Third Party Advisory
secalert@redhat.com

Source: CCN
Type: qemu-devel Web site
[PATCH] fdc: check drive block device before usage (CVE-2021-20196)

Source: CCN
Type: oss-sec Mailing List, Thu, 28 Jan 2021 12:29:04 +0530 (IST)
CVE-2021-20196 QEMU: block: fdc: null pointer dereference may lead to guest crash

Source: secalert@redhat.com
Type: Third Party Advisory
secalert@redhat.com

Source: secalert@redhat.com
Type: Mailing List, Patch, Third Party Advisory
secalert@redhat.com

Vulnerable Configuration:

Configuration RedHat 1:

cpe:/a:redhat:enterprise_linux:8:*:*:*:*:*:*:*

Configuration RedHat 2:

cpe:/a:redhat:enterprise_linux:8::appstream:*:*:*:*:*

Configuration RedHat 3:

cpe:/a:redhat:enterprise_linux:8::crb:*:*:*:*:*

Configuration CCN 1:

cpe:/a:qemu:qemu:-:*:*:*:*:*:*:*

Denotes that component is vulnerable

Oval Definitions

Definition ID	Class	Title	Last Modified
oval:com.redhat.rhsa:def:20221759	P	RHSA-2022:1759: virt:rhel and virt-devel:rhel security, bug fix, and enhancement update (Moderate)	2022-05-10
oval:org.opensuse.security:def:6005	P	Security update for qemu (Moderate)	2022-04-11
oval:org.opensuse.security:def:119099	P	Security update for qemu (Low)	2022-02-18
oval:org.opensuse.security:def:42190	P	Security update for qemu (Low)	2022-01-27
oval:org.opensuse.security:def:101607	P	Security update for qemu (Low)	2022-01-25
oval:org.opensuse.security:def:1669	P	Security update for qemu (Low)	2022-01-25
oval:org.opensuse.security:def:102239	P	Security update for qemu (Low)	2022-01-25
oval:org.opensuse.security:def:42290	P	Security update for qemu (Low)	2022-01-25
oval:org.opensuse.security:def:895	P	Security update for qemu (Low)	2022-01-25

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