SnapdApplication · Canonical
CVE-2020-11933
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 · uneditedcloud-init as managed by snapd on Ubuntu Core 16 and Ubuntu Core 18 devices was run without restrictions on every boot, which a physical attacker could exploit by crafting cloud-init user-data/meta-data via external media to perform arbitrary changes on the device to bypass intended security mechanisms such as full disk encryption. This issue did not affect traditional Ubuntu systems. Fixed in snapd version 2.45.2, revision 8539 and core version 2.45.2, revision 9659.
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 · high confidenceOn Ubuntu Core 16 and 18, cloud-init (managed by snapd) runs without restrictions on every boot. A physical attacker can insert external media containing crafted cloud-init user-data or meta-data, which cloud-init processes during boot. This allows arbitrary changes to the device to bypass security mechanisms such as full disk encryption.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
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
< 2.45.2
Ubuntu LinuxOperating system
= 16.04= 18.04= 19.10= 20.04CVSS 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
- Physical
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Check the installed Ubuntu versionRun 'lsb_release -r' or check '/etc/ubuntu-version' or '/etc/lsb-release'Affected if The version shows 16.04, 18.04, 19.10, or 20.04 (these are the affected versions)
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Check the snapd versionRun 'snap --version' or 'snapd --version' to retrieve the installed snapd version numberAffected if The snapd version is lower than 2.45.2 (or the revision is lower than 8539)
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Verify cloud-init is present and managedRun 'which cloud-init' or check if cloud-init package is installed via 'dpkg -l cloud-init'Affected if cloud-init is installed and the system uses it for early initialization (common on Ubuntu cloud images and Ubuntu Core)
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Check snapd service statusRun 'systemctl status snapd.service' or 'systemctl status snapd.socket' to verify snapd is runningAffected if snapd is active/running, as cloud-init is managed by snapd on affected Ubuntu Core systems
You are affected if you are running Ubuntu 16.04, 18.04, 19.10, or 20.04 with snapd version below 2.45.2, and an attacker with physical access could insert external media containing cloud-init data during boot to bypass security mechanisms.
Generated from the published advisory. Verify against your own configuration.
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.
From vendor data2.45.2
Upgrade snapd to version 2.45.2 (revision 8539) or later and core to version 2.45.2 (revision 9659) or later on Ubuntu Core devices. Avoid leaving external media connected during boot.
Fix this in Snapd
Scoped from the published advisory
- Consultation2.0 h
- Implementation4.0 h
- Testing6.0 h
- Review / QA3.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $4,096.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2020-11933 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2020-11933 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- 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
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