CVE-2017-18903
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 4.0.0, 3.10.2, and 3.9.2. CSRF can occur if CORS is 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 confidenceMattermost Server before versions 4.0.0, 3.10.2, and 3.9.2 contains a CSRF (Cross-Site Request Forgery) vulnerability that can be exploited when CORS (Cross-Origin Resource Sharing) is enabled. An attacker could potentially trick authenticated users into performing unintended actions on the Mattermost server by leveraging the CORS configuration.
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< 3.9.2>= 3.10.0, < 3.10.2CVSS 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 installationLocate the Mattermost Server binary or service. Common paths: /opt/mattermost/bin/mattermost, or check system services (systemctl status mattermost or similar).Affected if Mattermost Server is not installed or this is a different product (e.g., Mattermost Team Edition as a service, not the full Server).
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Determine installed Mattermost Server versionRun 'mattermost --version' or check the version file typically found in /opt/mattermost/version.txt, or look at the server startup logs.Affected if The version number is less than 3.9.2, or greater than or equal to 3.10.0 but less than 3.10.2, or less than 4.0.0 when comparing to the fixed versions.
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Locate Mattermost configuration fileThe config.json file is typically located in the config directory under the Mattermost installation path (e.g., /opt/mattermost/config/config.json).Affected if The configuration file cannot be found or accessed.
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Check if CORS is enabledOpen config.json and look for the 'ServiceSettings' section. Check for the 'EnableCORS' setting. If present, verify if it is set to true.Affected if EnableCORS is set to true in the ServiceSettings section of config.json.
The environment is affected if Mattermost Server version falls within < 3.9.2 or >= 3.10.0 and < 3.10.2, AND CORS (EnableCORS) is enabled in the configuration.
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 data3.9.23.10.2
Upgrade Mattermost Server to version 4.0.0, 3.10.2, 3.9.2 or later. If immediate upgrading is not feasible, disable CORS if not required for the deployment.
- Consultation2.0 h
- Implementation2.0 h
- Testing3.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2017-18903 — 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-2017-18903 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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