Nextcloud ServerApplication · Nextcloud
CVE-2020-8293
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 · uneditedA missing input validation in Nextcloud Server before 20.0.2, 19.0.5, 18.0.11 allows users to store unlimited data in workflow rules causing load and potential DDoS on later interactions and usage with those rules.
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 confidenceNextcloud Server lacks input validation on workflow rule configuration, allowing authenticated users to store unlimited/arbitrary data in workflow rules. This causes excessive resource consumption (CPU/memory) when these rules are processed during normal usage, leading to denial of service conditions.
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
Nextcloud ServerApplication
< 18.0.11>= 19.0.0, < 19.0.5>= 20.0.0, < 20.0.2CVSS 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
- Network
- Complexity
- Low
- Privileges
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/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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Determine installed Nextcloud Server versionLog in as administrator and navigate to Administration > Settings > Overview, or check the version file in your Nextcloud installation directory.Affected if The version displayed is below 18.0.11, or between 19.0.0 and 19.0.5, or between 20.0.0 and 20.0.2.
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Verify workflow app is enabledNavigate to Administration > Apps > Disabled apps, or use the occ command: occ app:list | grep workflow.Affected if The workflow engine or workflow_2 related app is listed as enabled.
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Check for existing workflow rulesNavigate to Settings > Workflow in the admin interface, or query the database table oc_flow_operations for any configured rules.Affected if There are workflow rules configured in the system.
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Review workflow rule configurations for sizeInspect the workflow rules in the admin interface or database to identify any rules with unusually large or repetitive configurations.Affected if Any workflow rule contains excessively large or unbounded configuration data.
You are affected if your Nextcloud Server version falls within the vulnerable ranges AND the workflow engine is enabled with configured rules that could contain arbitrary data.
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 data18.0.1119.0.520.0.2
Upgrade Nextcloud Server to version 20.0.2, 19.0.5, 18.0.11 or later which includes proper input validation for workflow rules.
Fix this in Nextcloud Server
Scoped from the published advisory
- Consultation4.0 h
- Implementation12.0 h
- Testing8.0 h
- Review / QA4.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $7,808.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2020-8293 — 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-2020-8293 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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