CVE-2021-4120

Name: CVE-2021-4120
Creator: NVD / NIST
Published: 2022-02-17T23:15:07.55+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 7.8/10EPSS 0.43%

Last modified Jun 17, 2026

CVE-2021-4120 is a high-severity vulnerability rated 7.8/10 on the CVSS scale. snapd 2.54.2 fails to perform sufficient validation of snap content interface and layout paths, resulting in the ability for snaps to inject arbitrary AppArmor policy rules via malformed content interface and layout declarations and hence escape strict snap confinement. Fixed in snapd versions 2.54.3+18.04, 2.54.3+20.04 and 2.54.3+21.10.1. EPSS estimates a 0.43% chance of exploitation in the next 30 days.

Description

snapd 2.54.2 fails to perform sufficient validation of snap content interface and layout paths, resulting in the ability for snaps to inject arbitrary AppArmor policy rules via malformed content interface and layout declarations and hence escape strict snap confinement. Fixed in snapd versions 2.54.3+18.04, 2.54.3+20.04 and 2.54.3+21.10.1

Metrics

CVSS 3.1

7.8/10

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

EPSS Probability

0.43%

34.4th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Canonical	Snapd	<= 2.54.2
Canonical	Ubuntu Linux	18.04
Canonical	Ubuntu Linux	20.04
Canonical	Ubuntu Linux	21.10
Fedoraproject	Fedora	34
Fedoraproject	Fedora	35

References

http://www.openwall.com/lists/oss-security/2022/02/18/2Exploit, Mailing List, Third Party Advisory
https://bugs.launchpad.net/snapd/+bug/1949368Exploit, Issue Tracking, Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/3QTBN7LLZISXIA4KU4UKDR27Q5PXDS2U/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/XCGHG6LJAVJJ72TMART6A7N4Z6MSTGI7/
https://ubuntu.com/security/notices/USN-5292-1Patch, Vendor Advisory
http://www.openwall.com/lists/oss-security/2022/02/18/2Exploit, Mailing List, Third Party Advisory
https://bugs.launchpad.net/snapd/+bug/1949368Exploit, Issue Tracking, Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/3QTBN7LLZISXIA4KU4UKDR27Q5PXDS2U/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/XCGHG6LJAVJJ72TMART6A7N4Z6MSTGI7/
https://ubuntu.com/security/notices/USN-5292-1Patch, Vendor Advisory

Timeline

Published: Feb 17, 2022
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-4120?

How severe is CVE-2021-4120?

CVE-2021-4120 has a CVSS score of 7.8/10 (HIGH severity). The EPSS model estimates a 0.43% probability of exploitation in the next 30 days.

How do I fix CVE-2021-4120?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-4120?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST