CVE-2019-20882
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 5.8.0. It does not honor the domain requirement when processing a join request for an open team.
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 5.8.0 fails to enforce configured email domain restrictions when processing join requests for open teams. This allows users from any email domain to join teams that should be restricted to specific domains, bypassing the intended access control policy.
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< 5.8.0CVSS 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
- Low
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/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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Check Mattermost Server versionRun 'grep -i version /opt/mattermost/version.go' or access the System Console and navigate to 'About' > 'Mattermost' to view the version numberAffected if The installed version is earlier than 5.8.0
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Verify email domain restrictions are configuredIn System Console, navigate to 'Authentication' > 'Email' and check if 'Restrict signup to email domain' is set to a specific domainAffected if Email domain restrictions are configured (a domain is specified in the restriction field)
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Identify open teams in the systemIn System Console, go to 'Teams' and review each team's 'Allow any account with @domain.com' setting, or use the mattermost CLI: 'mattermost team list' and check team settings for opennessAffected if There are teams configured as 'open' (allowing anyone to join without invitation)
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Confirm restriction bypass conditionA user from a non-restricted domain attempts to join a restricted team that is set to open membership, or review system logs for join events from unauthorized domainsAffected if Users from domains not in the restriction list can successfully join teams that have domain restrictions configured
You are affected if running Mattermost Server versions earlier than 5.8.0 AND have teams configured with both email domain restrictions and open membership settings, as users from unauthorized domains can bypass the restrictions to join these teams.
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 data5.8.0
Upgrade to Mattermost Server 5.8.0 or later. Until then, avoid using open team settings when domain restrictions are required, or implement additional access controls at the infrastructure level.
- Consultation3.0 h
- Implementation6.0 h
- Testing4.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2019-20882 — 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-2019-20882 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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