CVE-2021-4120Public exploit

Confinement escape via malformed AppArmor policy paths

Published Feb 17, 2022 · Updated Aug 3, 2024

Improper path validation in Canonical snapd 2.54.2 and earlier allows local users to escape strict snap confinement. Content-interface and layout declarations accept malformed paths that are embedded as arbitrary AppArmor policy rules in a snap's generated profile. Exploitation requires installing and running a crafted snap locally; the injected rules grant access outside the snap sandbox.

CVSS severity8.2
High
EPSS probability0.44%
Next 30 days · Sep 17, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper path validation in Canonical snapd 2.54.2 and earlier allows local users to escape strict snap confinement. Content-interface and layout declarations accept malformed paths that are embedded as arbitrary AppArmor policy rules in a snap's generated profile. Exploitation requires installing and running a crafted snap locally; the injected rules grant access outside the snap sandbox.

The record

CVE
CVE-2021-4120
Published
Feb 17, 2022
Updated
Aug 3, 2024
Vendor
Canonical
Product
snapd
Classifications
CWE-20, T1611
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Feb 17, 2022CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=unspecified <=2.54.2

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Canonical · snapdversion=unspecified <=2.54.2

Published CVSS scores

7.8NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
8.2CanonicalCVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H
4.6NIST NVDAV:L/AC:L/Au:N/C:P/I:P/A:P

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-20Improper Input Validation
T1611Escape to Host

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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