CVE-2021-4120: snapd could be made to bypass intended access restrictions through snap content interfaces and layout paths

Severity: high (CVSS 7.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2022-02-17 · updated 2026-06-17
Weakness: CWE-20

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

Affected products

Canonical Ltd. snapd: through 2.54.2
Canonical Ubuntu Linux: 18.04, 20.04, 21.10
Fedoraproject Fedora: 34, 35

References

http://www.openwall.com/lists/oss-security/2022/02/18/2
https://bugs.launchpad.net/snapd/+bug/1949368
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-5292-1
http://www.openwall.com/lists/oss-security/2022/02/18/2
https://bugs.launchpad.net/snapd/+bug/1949368
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-5292-1

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