dbcve.org
Mattermost ServerApplication · Mattermost

CVE-2017-18915

CRITICAL · 9.8 CVSS v3.1 Published 2020-06-19
Fix available
A fix is available. Upgrade to 3.6.7 / 3.7.5 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

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 · unedited
An issue was discovered in Mattermost Server before 3.8.2, 3.7.5, and 3.6.7. After a restart of a server, an attacker might suddenly gain API Endpoint access.

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 confidence

A vulnerability in Mattermost Server allows unauthorized API endpoint access after a server restart. The issue appears to be related to improper session or authentication state handling during the restart process, potentially allowing attackers to bypass authentication controls and gain API access with network reachability.

MitigationUpgrade Mattermost Server to version 3.8.2, 3.7.5, or 3.6.7 or later. If immediate patching is not possible, restrict network access to the API endpoints and monitor for unauthorized access attempts, especially during or after server restarts.

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
Mattermost ServerApplication
Affected:>= 3.6.0, < 3.6.7>= 3.7.0, < 3.7.5>= 3.8.0, < 3.8.2

CVSS 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
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/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 checks

Work through these to decide whether this CVE applies to you.

  1. Identify Mattermost Server version
    Access the Mattermost System Console and navigate to About > Mattermost, or use the CLI command 'mattermost version' if you have server access. Record the exact version number displayed.
    Affected if The version falls within these ranges: 3.6.0 through 3.6.6, 3.7.0 through 3.7.4, or 3.8.0 through 3.8.1.
  2. Confirm network accessibility of API endpoints
    Determine whether the Mattermost API (typically at /api/v3/ or /api/v4/ paths) is accessible from untrusted networks. Check your firewall rules, reverse proxy configuration, or cloud security group settings that control inbound access to the server on ports 80 or 443.
    Affected if The API endpoints are reachable from network locations outside your trusted administrative zone.
  3. Review server restart logs
    Examine Mattermost server logs for the time period surrounding any restarts. Look for API access events that occurred immediately after restart events, particularly from sources that should not have had prior authentication.
    Affected if API requests were successfully authenticated or accepted without proper credentials shortly after a server restart.

You are affected if your Mattermost Server version is 3.6.0-3.6.6, 3.7.0-3.7.4, or 3.8.0-3.8.1 AND your API endpoints are accessible from the network.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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 · scoped
Upgrade available Upgrade to 3.6.7 / 3.7.5 / 3.8.2 or later
Fixed in 3.6.73.7.53.8.2
Interim mitigation

Upgrade Mattermost Server to version 3.8.2, 3.7.5, or 3.6.7 or later. If immediate patching is not possible, restrict network access to the API endpoints and monitor for unauthorized access attempts, especially during or after server restarts.

Recommended fix High confidence

Mattermost Server 3.8.2 (or 3.7.5 for 3.7.x branch, or 3.6.7 for 3.6.x branch)

  1. 1. Back up your Mattermost Server database and configuration files before proceeding with the upgrade.
  2. 2. Stop the Mattermost Server service to prevent data corruption during upgrade.
  3. 3. Upgrade Mattermost Server to version 3.8.2 (or at minimum to your branch's fixed version: 3.6.7 for 3.6.x, 3.7.5 for 3.7.x, or 3.8.2 for 3.8.x).
  4. 4. Verify the upgrade was successful by checking the server version in the system console.
  5. 5. Start the Mattermost Server service.
  6. 6. After restart, verify that API access controls are properly enforced and unauthorized access is no longer possible.
Caveat Review migration guide for your upgrade path; major version jumps may require schema updates and have compatibility considerations

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Mattermost Server Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing6.0 h
  • Review / QA3.0 h
15.0 hours of engineering $2,560
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $4,096.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2017-18915 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2017-18915 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

What this is

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.

What belongs here
  • 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