CVE-2019-20859
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 5.15.0. Login access control can be bypassed via crafted input.
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 version 5.15.0 contains a login access control bypass vulnerability where crafted input can circumvent authentication mechanisms, allowing unauthorized access to user accounts.
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
- High
- Integrity
- None
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/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 installed Mattermost Server versionAccess the Mattermost System Console and navigate to About > Mattermost, or use the command line: grep -i 'BuildNumber' /opt/mattermost/config/config.json 2>/dev/null || cat /opt/mattermost/version.txt 2>/dev/nullAffected if The version displayed is less than 4.10.8, or falls between 5.7.0-5.7.2, 5.8.0-5.8.0, or equals 5.9.0
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Confirm authentication is enabledVerify the Mattermost server has user authentication mechanisms configured and active by checking /opt/mattermost/config/config.json for 'EnableSignInWithEmail': true or similar authentication settingsAffected if User login and authentication are enabled and the server version is within the affected ranges listed in step 1
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Check if server is exposed to networkReview network configuration to determine if the Mattermost login endpoint is accessible from network segments where untrusted input could be submittedAffected if The authentication endpoint is network-accessible and the installed version is among the affected versions
You are affected if your Mattermost Server version is less than 4.10.8, between 5.7.0-5.7.2, between 5.8.0-5.8.0, or exactly 5.9.0, and user authentication is enabled on the server.
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 5.15.0 or later to obtain the security fix. If immediate upgrading is not possible, implement additional authentication safeguards such as account lockout policies and enhanced input validation at the application perimeter.
- Consultation3.0 h
- Implementation4.0 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-2019-20859 — 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-2019-20859 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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