CVE-2019-20841
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 5.18.0, 5.17.2, 5.16.4, 5.15.4, and 5.9.7. CSRF can sometimes occur via a crafted web site for account takeover attacks.
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 confidenceA Cross-Site Request Forgery (CSRF) vulnerability in Mattermost Server allows authenticated users to have their sessions exploited via malicious websites. Attackers can craft malicious pages that silently submit requests to the Mattermost server using the victim's active session, potentially leading to unauthorized account actions or account takeover.
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< 5.9.7>= 5.15.0, < 5.15.4>= 5.16.0, < 5.16.4>= 5.17.0, < 5.17.2= 5.18.0CVSS 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
- Required
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/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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Identify Mattermost Server versionLocate the installed version of Mattermost Server through the system console (usually found under Site Statistics or about section) or by checking the server configuration files and logs where the version is typically displayed on startup or in the diagnostic outputAffected if The installed version matches one of the affected ranges: < 5.9.7, >= 5.15.0 and < 5.15.4, >= 5.16.0 and < 5.16.4, >= 5.17.0 and < 5.17.2, or exactly version 5.18.0
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Verify CSRF protection configurationInspect the Mattermost Server configuration file (config.json) or the system console settings for CSRF token enforcement and SameSite cookie attributes. These settings control whether the server validates CSRF tokens on state-changing requests.Affected if The server is running an affected version and the CSRF protection is not properly enforced (though in vulnerable versions, the protection is inadequate by default)
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Confirm active user sessions existReview the system to confirm that user authentication is enabled and users have active sessions. CSRF attacks require authenticated sessions to exploit, so check if the server has enabled user authentication and has active user accounts.Affected if The server is running an affected version AND has user authentication enabled with active authenticated sessions
A server is affected if it runs any Mattermost Server version in the ranges < 5.9.7, >= 5.15.0 to < 5.15.4, >= 5.16.0 to < 5.16.4, >= 5.17.0 to < 5.17.2, or exactly 5.18.0, and has user authentication enabled with active sessions.
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 data5.9.75.15.45.16.4
Upgrade Mattermost Server to version 5.18.0, 5.17.2, 5.16.4, 5.15.4, 5.9.7 or later. These versions include proper CSRF token validation and SameSite cookie attributes to prevent cross-origin request forgery.
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA3.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2019-20841 — 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-2019-20841 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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A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.
- 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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