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SnapdApplication · Canonical

CVE-2021-3155

MEDIUM · 5.5 CVSS v3.1 Published 2022-02-17
Fix available
A fix is available. Upgrade to 2.54.3 or later.
See remediation →
57/100
Remediation priority · Elevated
Zero-click Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
snapd 2.54.2 and earlier created ~/snap directories in user home directories without specifying owner-only permissions. This could allow a local attacker to read information that should have been private. Fixed in snapd versions 2.54.3+18.04, 2.54.3+20.04 and 2.54.3+21.10.1

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis
How this class of weakness works · CWE-276

Files, directories, or resources ship with permissions more open than they need to be, so unintended users can read or modify them. Attackers look for exactly these loose defaults. Remediation means tightening permissions to the minimum required and verifying them at install and at runtime.

General guidance for the incorrect default permissions class — the official description and references above are authoritative for this specific CVE. Want a bespoke review and a reviewed fix? Ask our team →

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
SnapdApplication
Affected:< 2.54.3
Ubuntu LinuxOperating system
Affected:= 18.04= 20.04= 21.10

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

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

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 2.54.3 or later
Fixed in 2.54.3
Vendor patch github.com →
Recommended fix High confidence

snapd >= 2.54.3 (Ubuntu: 2.54.3+18.04, 2.54.3+20.04, or 2.54.3+21.10.1)

  1. 1. Check current snapd version: snapd --version or snap version
  2. 2. Update snapd package via system package manager: sudo apt update && sudo apt upgrade snapd (for Ubuntu/Debian)
  3. 3. Alternatively, refresh snap packages: sudo snap refresh
  4. 4. Verify the installed snapd version is 2.54.3 or higher
  5. 5. For existing ~/snap directories, manually fix permissions if needed: chmod 700 ~/snap (owner read/write/execute only)

Generated from the published advisory — verify against the referenced sources before acting.

We can perform the upgrade in your staging environment and verify nothing breaks — typical engagement from $900. Get the upgrade done

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-3155 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data