CVE-2019-20860
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 · uneditedAn issue was discovered in Mattermost Server before 5.14.0, 5.13.3, 5.12.6, and 5.9.4. It allows remote attackers to cause a denial of service (application hang) via a crafted SVG document.
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 confidenceMattermost Server fails to properly validate uploaded SVG files, allowing remote attackers to upload a specially crafted SVG document that causes the application to hang and become unresponsive, resulting in denial of service.
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< 5.9.4>= 5.12.0, < 5.12.6>= 5.13.0, < 5.13.3= 5.14.0CVSS 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
- None
- User interaction
- Required
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/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 Mattermost Server versionLog into the Mattermost System Console and navigate to Environment > Performance, or run 'mattermost version' from the command line if you have CLI access.Affected if The installed version falls within < 5.9.4, >= 5.12.0 to < 5.12.6, >= 5.13.0 to < 5.13.3, or equals exactly 5.14.0.
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Confirm SVG file uploads are permittedIn the System Console, go to Posts > Files > Images and check if SVG files are enabled in the allowed file extensions or MIME type settings. Alternatively, inspect the service configuration file (config.json) for allowed file types.Affected if SVG file uploads are not explicitly blocked or restricted in the file upload configuration.
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Verify the server is exposed to unauthenticated or authenticated file uploadCheck if the file upload endpoint is accessible to users. Review the authentication settings under Authentication > Email or any SSO configuration to determine if unauthenticated users can upload files.Affected if The upload functionality is accessible to users without additional file type validation at the proxy or application layer.
You are affected if your Mattermost Server version is vulnerable AND SVG file uploads are permitted on your instance.
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 data5.9.45.12.65.13.3
Upgrade Mattermost Server to version 5.14.0, 5.13.3, 5.12.6, or 5.9.4 or later. Additionally, implement file type validation and size limits for SVG uploads at the application or web server level as a defense-in-depth measure.
- Consultation1.0 h
- Implementation2.0 h
- Testing2.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2019-20860 — 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-2019-20860 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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