CVE-2021-4120: snapd 2.54.2 fails to perform sufficient validation of snap content interface and layout paths, resulting in t

Q: How do I fix CVE-2021-4120?

snapd: upgrade to newer than 2.54.2; ubuntu linux: mitigate or apply the listed mitigation; fedora: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Q: Is CVE-2021-4120 being exploited?

CVE-2021-4120 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2021-4120 affect?

CVE-2021-4120 affects snapd, ubuntu linux, fedora. Severity is high (CVSS 8.2). 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 e

Q: How urgent is CVE-2021-4120?

Priority 48/100. High severity; Public exploit reference; On your watchlist

This month

HIGH 8.2WATCHLISTUPGRADEMITIGATEMITIGATE

CVE-2021-4120 is a high-severity flaw (CVSS 8.2) affecting snapd, ubuntu linux, fedora. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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

Why this priority

High severity
Public exploit reference
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	8.2 (High)
Attack vector	Local
Attack complexity	Low
Privileges needed	Low
User interaction	Required
EPSS exploit chance	0.4% (top 62%)
CISA exploited list	No
Weakness	CWE-20
Published	2022-02-17
Last modified	2026-06-17

Publisher (CNA): Canonical Ltd. · Vendor: canonical · fedoraproject

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2022-02-17 23:15 UTCPublished CVE record published
2026-06-17 04:19 UTCUpdated Record last modified

canonical snapd UPGRADE

Affected: <= 2.54.2

Fixed in: newer than 2.54.2

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy snapd || rpm -q snapd || snapd --version

2. UPGRADE to newer than 2.54.2 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade snapd

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade snapd

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

canonical ubuntu linux MITIGATE

Affected: 18.04 · 20.04 · 21.10

Fixed in: no fixed release known

Safe to downgrade to: a release before 18.04

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

fedoraproject fedora MITIGATE

Affected: 34 · 35

Fixed in: no fixed release known

Safe to downgrade to: a release before 34

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2021-4120?

snapd: upgrade to newer than 2.54.2; ubuntu linux: mitigate or apply the listed mitigation; fedora: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2021-4120 being exploited?

CVE-2021-4120 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2021-4120 affect?

CVE-2021-4120 affects snapd, ubuntu linux, fedora. Severity is high (CVSS 8.2). 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 e

How urgent is CVE-2021-4120?

Priority 48/100. High severity; Public exploit reference; On your watchlist

Software pages

Ubuntu vulnerabilities

Related CVEs

CVE-2024-5138 HIGH 8.1 UPGRADE The snapctl component within snapd allows a confined snap to interact with the snapd daemon to take certain pr
CVE-2024-29069 MEDIUM 4.8 UPGRADE In snapd versions prior to 2.62, snapd failed to properly check the destination of symbolic links when extract
CVE-2024-29068 MEDIUM 5.8 UPGRADE In snapd versions prior to 2.62, snapd failed to properly check the file type when extracting a snap
CVE-2024-1724 MEDIUM 6.3 UPGRADE In snapd versions prior to 2.62, when using AppArmor for enforcement of sandbox permissions, snapd failed to
CVE-2023-1523 CRITICAL 10.0 UPGRADE MITIGATE Using the TIOCLINUX ioctl request, a malicious snap could inject contents into the input of the controlling te

References

← Back to latest CVEs