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Mattermost ServerApplication · Mattermost

CVE-2023-45847

HIGH · 7.5 CVSS v3.1 Published 2023-12-12
Fix available
A fix is available. Upgrade to after 9.2.1 or later.
See remediation →
84/100
Remediation priority · High
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
Mattermost fails to to check the length when setting the title in a run checklist in Playbooks, allowing an attacker to send a specially crafted request and crash the Playbooks plugin

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

Mattermost Playbooks plugin lacks proper length validation on the title field in run checklists, allowing authenticated attackers to send specially crafted requests with excessively long titles that cause the plugin to crash, resulting in denial of service.

MitigationApply input validation bounds checking on the title parameter in the Playbooks run checklist API endpoint to enforce reasonable length limits before processing.

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:<= 7.8.14>= 8.0.0, <= 8.1.5>= 9.0.0, <= 9.0.3>= 9.1.1, <= 9.1.2>= 9.2.0, <= 9.2.1

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
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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
    Run 'mattermost version' from the command line, or check the /api/v4/system/config endpoint, or view the system console about page
    Affected if The installed version falls within <= 7.8.14; >= 8.0.0 and <= 8.1.5; >= 9.0.0 and <= 9.0.3; >= 9.1.1 and <= 9.1.2; >= 9.2.0 and <= 9.2.1
  2. Confirm Playbooks plugin is enabled
    Check the system console plugins management page, or query the /api/v4/plugins endpoint for the playbooks plugin status
    Affected if The Playbooks plugin is installed and active in the Mattermost environment
  3. Verify API access for run checklist operations
    Check that the /api/v1/playbooks/{id}/runs/{run_id}/checklist endpoint is accessible to authenticated users through the API
    Affected if Authenticated users can access the Playbooks run checklist API endpoints without additional restrictions
  4. Review recent plugin crash logs
    Examine Mattermost server logs (typically in /var/log/mattermost or via 'mattermost logs') for crash or panic events related to the Playbooks plugin occurring around checklist title operations
    Affected if Logs show plugin crashes correlating with long title field submissions in checklist items

The environment is affected if Mattermost Server is running a version within the affected ranges AND the Playbooks plugin is enabled and accessible to authenticated users.

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 a release after 9.2.1
Interim mitigation

Apply input validation bounds checking on the title parameter in the Playbooks run checklist API endpoint to enforce reasonable length limits before processing.

Recommended fix Moderate confidence

Upgrade to the latest patch release in your major version branch: 7.8.15+, 8.1.6+, 9.0.4+, or 9.1.3+ (or the latest 9.x release if available)

  1. 1. Identify the currently installed Mattermost Server version by checking the system console or running 'mattermost version'
  2. 2. Based on your current major version, upgrade to the minimum fixed patch release: For 7.8.x branch, upgrade to 7.8.15 or later; For 8.0.x-8.1.x branch, upgrade to 8.1.6 or later; For 9.0.x branch, upgrade to 9.0.4 or later; For 9.1.x branch, upgrade to 9.1.3 or later
  3. 3. Review Mattermost upgrade documentation for your deployment type (debian/apt, yum/rpm, docker, or helm chart)
  4. 4. Perform a backup of the database and configuration files before upgrading
  5. 5. Follow the standard upgrade procedure for your deployment method
  6. 6. After upgrade, verify the Playbooks plugin is functioning correctly by creating a test playbook with a checklist item
  7. 7. Monitor system logs to confirm no crashes occur from specially crafted Playbook requests
Caveat Standard Mattermost minor version upgrades may include deprecations; review release notes for your target version for any configuration or API changes

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
  • Testing3.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,930
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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-2023-45847 in production — separate from our analysis above.

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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