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Mattermost ServerApplication · Mattermost

CVE-2023-3593

MEDIUM · 6.5 CVSS v3.1 Published 2023-07-17
Fix available
A fix is available. Upgrade to 7.8.7 / 7.9.5 or later.
See remediation →
71/100
Remediation priority · Elevated
Remotely reachable 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 properly validate markdown, allowing an attacker to crash the server via a specially crafted markdown input.

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 contains a vulnerability in its markdown processing where input validation is insufficient. A remote attacker can submit a specially crafted markdown payload that triggers a server crash through improper handling of the malformed input.

MitigationApply available patches for CVE-2023-3593 when released. Until then, consider restricting or sanitizing markdown input from untrusted sources and monitor for server availability issues.

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:>= 7.8.0, < 7.8.7>= 7.9.0, < 7.9.5>= 7.10.0, < 7.10.3

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
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:L/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 installation
    Check if Mattermost Server is installed by looking for the mattermost executable or service: which mattermost or systemctl list-units | grep mattermost
    Affected if Mattermost Server is not present on the system
  2. Determine installed Mattermost version
    Run 'mattermost version' or check the version file typically located in /opt/mattermost/version.txt
    Affected if The installed version falls within any of these ranges: 7.8.0-7.8.6, 7.9.0-7.9.4, or 7.10.0-7.10.2
  3. Verify markdown input is accepted
    Check if the Mattermost server accepts markdown in posts, messages, or comments through the web UI or API endpoint /api/v4/posts
    Affected if Markdown input processing is enabled (this is the default behavior)
  4. Confirm server is exposed to untrusted input
    Review Mattermost configuration file config.json for 'AllowCors' settings and network exposure, or check if the server accepts posts from non-authenticated users or guest accounts
    Affected if The server accepts markdown from users who are not fully trusted or from external sources

A user is affected if Mattermost Server is running a version between 7.8.0-7.8.6, 7.9.0-7.9.4, or 7.10.0-7.10.2 and the server processes markdown input from potentially untrusted sources.

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 7.8.7 / 7.9.5 / 7.10.3 or later
Fixed in 7.8.77.9.57.10.3
Interim mitigation

Apply available patches for CVE-2023-3593 when released. Until then, consider restricting or sanitizing markdown input from untrusted sources and monitor for server availability issues.

Recommended fix High confidence

Upgrade to 7.8.7 (for 7.8.x), 7.9.5 (for 7.9.x), or 7.10.3 (for 7.10.x) - or latest stable 7.x release

  1. Backup the Mattermost server database and configuration files
  2. Schedule a maintenance window as the upgrade may require server restart
  3. For Mattermost 7.8.x: Upgrade to version 7.8.7 or later (recommended: latest stable 7.x release)
  4. For Mattermost 7.9.x: Upgrade to version 7.9.5 or later (recommended: latest stable 7.x release)
  5. For Mattermost 7.10.x: Upgrade to version 7.10.3 or later (recommended: latest stable 7.x release)
  6. Download the appropriate Mattermost Server package from https://mattermost.com/download/
  7. Follow the official Mattermost upgrade guide to apply the update: https://docs.mattermost.com/upgrade/upgrade-mattermost.html
  8. After upgrade, verify the server is running and test markdown rendering functionality
Caveat Standard Mattermost upgrade considerations apply: review release notes for any breaking changes, backup before upgrading

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 / QA1.0 h
10.0 hours of engineering $1,750
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,800.

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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-2023-3593 in production — separate from our analysis above.

No notes yet

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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