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Fencer Vulns
high 8.2

CVE-2021-4120 json

snapd could be made to bypass intended access restrictions through snap content interfaces and layout paths

published 2022-02-17 4 y ago modified 2026-06-17 4 mo ago also EUVD-2021-33996

cvss
8.2
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 38%
public exploits
0
none known

Summary

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

Patch / fix

  • snapd Debian 14, Debian 13, Debian 12 2.54.3-1

debian advisories DEBIAN-CVE-2021-4120

  • snapd Ubuntu 18.04 LTS 2.54.3+18.04
  • snapd Ubuntu 20.04 LTS 2.54.3+20.04.1
  • snapd Ubuntu Pro 14.04 LTS 2.54.3+14.04~esm1
  • snapd Ubuntu Pro 16.04 LTS 2.54.3+16.04~esm2

ubuntu advisories UBUNTU-CVE-2021-4120

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2021-4120 updated cvss 8.2

snapd: Insufficient validation of snap content interface and layout paths

  • Red Hat All currently supported Red Hat products
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

0.44% chance of exploitation in the next 30 days, higher than 38% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • bugs.launchpad.net https://bugs.launchpad.net/snapd/+bug/1949368 referenced PoC, tagged "exploit" by a source, unverified
  • openwall.com http://www.openwall.com/lists/oss-security/2022/02/18/2 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 8.2 CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H
NVD 3.1 7.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 4.6 AV:L/AC:L/Au:N/C:P/I:P/A:P

Affected products

  • Canonical Ltd. snapd

Classification

Weakness
  • CWE-20 Improper Input Validation

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.