CVE-2025-20033
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 · uneditedMattermost versions 10.2.0, 9.11.x <= 9.11.5, 10.0.x <= 10.0.3, 10.1.x <= 10.1.3 fail to properly validate post types, which allows attackers to deny service to users with the sysconsole_read_plugins permission via creating a post with the custom_pl_notification type and specific props.
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 fails to properly validate post types in versions 10.2.0, 9.11.x <= 9.11.5, 10.0.x <= 10.0.3, and 10.1.x <= 10.1.3. An attacker with the sysconsole_read_plugins permission can create a post with the custom_pl_notification type and specific props, triggering a denial of service condition.
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>= 9.11.0, < 9.11.6>= 10.0.0, < 10.0.4>= 10.1.0, < 10.1.4>= 10.2.0, < 10.2.1CVSS 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 checksWork through these to decide whether this CVE applies to you.
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Identify your Mattermost Server versionAccess the Mattermost System Console or check the server's about page (usually at /api/v4/system/about). Look for the version number in the format X.Y.ZAffected if The installed version falls within any of these ranges: 9.11.0 through 9.11.5, 10.0.0 through 10.0.3, 10.1.0 through 10.1.3, or 10.2.0 (exact version without patch)
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Check for sysconsole_read_plugins permission assignmentsQuery your Mattermost database or API for roles and permissions, specifically looking for the sysconsole_read_plugins permission. Use the Mattermost API endpoint /api/v4/roles or inspect role permissions in the database.Affected if Any user role that includes sysconsole_read_plugins is assigned to untrusted or non-admin users, or if any user outside the trusted admin group has this permission
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Examine recent posts for custom_pl_notification typeQuery the Posts table in the Mattermost database or use the API to search for posts where the type field equals 'custom_pl_notification'. Check the post props for any unusual or crafted values.Affected if Any posts exist in the system with post type set to custom_pl_notification, especially if they contain unexpected props that may indicate exploitation attempts
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Review server logs for post validation errorsCheck Mattermost server logs (typically in /var/log/mattermost or the configured log location) for entries related to post type validation, custom_pl_notification processing, or denial of service errors around post creation.Affected if Logs show errors, exceptions, or service disruptions related to custom_pl_notification post types being processed
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Verify plugin-related system console accessIn the Mattermost System Console, navigate to the Plugins section and verify which users or roles have access to view installed plugins. Check the list of users with System Console read access.Affected if Users other than system administrators have access to view the plugin management section in the system console, indicating they hold the sysconsole_read_plugins permission
You are affected if your Mattermost Server version is 9.11.0-9.11.5, 10.0.0-10.0.3, 10.1.0-10.1.3, or exactly 10.2.0 AND any user with the sysconsole_read_plugins permission (including non-admins) exists in your system.
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 · scoped9.11.610.0.410.1.4
Upgrade to a patched Mattermost version beyond 10.2.0, 9.11.5, 10.0.3, and 10.1.3, or restrict the sysconsole_read_plugins permission from untrusted users until a patch is available.
Upgrade to 9.11.6, 10.0.4, 10.1.4, or 10.2.1 depending on your current branch
- Identify the currently installed Mattermost Server version using the system console or CLI
- If running 9.11.0 <= version < 9.11.6, upgrade to version 9.11.6
- If running 10.0.0 <= version < 10.0.4, upgrade to version 10.0.4
- If running 10.1.0 <= version < 10.1.4, upgrade to version 10.1.4
- If running 10.2.0, upgrade to version 10.2.1
- After upgrade, verify the server is operational and test that the fix prevents the DoS condition
- Review release notes for any additional security fixes included in the upgrade
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation4.0 h
- Testing2.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2025-20033 — 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-2025-20033 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
- No spam, self-promotion, credentials, or personal data