CVE-2019-20863
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 5.13.0. Incoming webhook creation is not properly restricted.
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 · moderate confidenceMattermost Server before 5.13.0 has a broken access control vulnerability where incoming webhook creation is not properly restricted. This likely allows unauthorized users (potentially any authenticated user) to create incoming webhooks that can post messages to channels, which could be exploited for data exfiltration or social engineering attacks.
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< 5.13.0CVSS 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
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- High
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
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 Mattermost Server versionAccess the Mattermost System Console and navigate to About > Mattermost, or use the command line: mmctl version or check the /opt/mattermost/version fileAffected if The version displayed is below 5.13.0
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Verify webhook permissions configurationNavigate to System Console > Integrations > Integration Management and confirm whether the settings 'Enable Incoming Webhooks' and 'Allow users to create incoming webhooks' are restricted to specific roles or channelsAffected if Webhook creation is not restricted to authorized administrators or specific channel roles
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Review existing incoming webhooksNavigate to System Console > Integrations > Incoming Webhooks and enumerate all configured webhooksAffected if Any incoming webhooks exist that were not created by system administrators
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Examine audit logs for webhook creationNavigate to System Console > Audit Logs and filter for events related to webhook creation (e.g., 'create_incoming_webhook')Affected if Audit logs show webhook creation events from users who should not have permission to create webhooks
The environment is affected if the installed Mattermost Server version is below 5.13.0, as the broken access control allows unauthorized webhook creation.
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 data5.13.0
Upgrade Mattermost Server to version 5.13.0 or later which contains the proper restrictions for webhook creation. Also review existing webhook configurations and audit logs for any unauthorized webhooks that may have been created.
- Consultation2.0 h
- Implementation4.0 h
- Testing3.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2019-20863 — 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-2019-20863 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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