CVE-2017-18911
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 3.8.2, 3.7.5, and 3.6.7. The X.509 certificate validation can be skipped for a TLS-based e-mail server.
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 confidenceMattermost Server fails to validate X.509 certificates when establishing TLS connections to email servers. This allows a man-in-the-middle attacker to intercept sensitive email credentials and communications by presenting a fraudulent certificate.
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< 3.6.7>= 3.7.0, < 3.7.5>= 3.8.0, < 3.8.2CVSS 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
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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 versionAccess the Mattermost System Console or use the API endpoint /api/v4/system/stats to retrieve the server version informationAffected if The installed version is < 3.6.7, or >= 3.7.0 and < 3.7.5, or >= 3.8.0 and < 3.8.2
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Verify email server configuration existsLocate the email configuration file (config.json) or navigate to the Email section in the System Console to confirm an SMTP/email server is configuredAffected if An email server is configured with host, port, and credentials set
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Confirm TLS is enabled for email connectionsInspect the email configuration settings in config.json or the System Console. Look for the EnableSMTPAuth field, the connection security settings, and whether the server URL uses port 465 or 587 with TLS enabledAffected if TLS or SSL is enabled for the email server connection and the server version falls within the affected ranges above
You are affected if your Mattermost Server version is one of the vulnerable versions listed AND you have an email server configured with TLS enabled for outgoing mail connections.
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.
dbcve · scoped3.6.73.7.53.8.2
Upgrade Mattermost Server to version 3.8.2, 3.7.5, or 3.6.7 or later, which includes proper certificate validation for email server TLS connections.
Upgrade to Mattermost Server 3.8.2 (or 3.7.5/3.6.7 depending on your current version branch)
- 1. Back up the Mattermost Server database and configuration files
- 2. Review Mattermost upgrade documentation for your current version
- 3. Plan maintenance window for the upgrade process
- 4. Stop the Mattermost Server service
- 5. Upgrade to the appropriate fixed version: 3.8.2 (recommended), 3.7.5, or 3.6.7 depending on your current branch
- 6. Verify the upgrade completed successfully
- 7. Restart the Mattermost Server service
- 8. Confirm TLS email server connections are now properly validating X.509 certificates
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation2.0 h
- Testing2.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,984.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2017-18911 — 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-2017-18911 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
- No spam, self-promotion, credentials, or personal data