CVE-2019-20877
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 5.9.0, 5.8.1, 5.7.3, and 4.10.8. It allows attackers to obtain sensitive information about whether someone has 2FA enabled.
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 confidenceAn information disclosure vulnerability in Mattermost Server allows attackers to determine whether specific users have two-factor authentication (2FA) enabled by observing differences in server responses to certain authentication queries. This enables user 2FA status enumeration.
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< 4.10.8>= 5.7.0, < 5.7.3>= 5.8.0, < 5.8.1= 5.9.0CVSS 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
- Low
- Integrity
- None
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/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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Identify Mattermost Server versionLog into the Mattermost System Console and navigate to About > Mattermost, or run 'mattermost version' from the command line, or query the /api/v4/system endpointAffected if The version displayed is < 4.10.8, or between 5.7.0 and 5.7.2 inclusive, or 5.8.0, or exactly 5.9.0
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Verify the exact version numberConfirm the full version string including patch number (for example, 5.7.2 vs 5.7.0)Affected if The version falls within any of the affected ranges listed above
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Confirm Mattermost is exposed to networkDetermine if the Mattermost server authentication endpoints are reachable from untrusted networksAffected if The server is internet-facing or accessible to users outside the trusted internal network
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Check for rate limiting on auth endpointsReview Mattermost configuration for rate limit settings on /api/v4/users/login and similar authentication endpointsAffected if Rate limiting is not configured or is set to allow unlimited requests
You are affected if your Mattermost Server version matches any of the affected ranges: < 4.10.8, >= 5.7.0 and < 5.7.3, >= 5.8.0 and < 5.8.1, or exactly 5.9.0.
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 data4.10.85.7.35.8.1
Upgrade Mattermost Server to version 5.9.0, 5.8.1, 5.7.3, 4.10.8, or later. Additionally, implement rate limiting on authentication endpoints to hinder automated enumeration attempts.
- Consultation2.0 h
- Implementation2.0 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-2019-20877 — 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-2019-20877 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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