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Mattermost ServerApplication · Mattermost

CVE-2024-36255

MEDIUM · 5.7 CVSS v3.1 Published 2024-05-26
Fix available
A fix is available. Upgrade to 8.1.13 / 9.5.4 or later.
See remediation →
61/100
Remediation priority · Elevated
Remotely reachable

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 versions 9.5.x <= 9.5.3, 9.6.x <= 9.6.1 and 8.1.x <= 8.1.12 fail to perform proper input validation on post actions which allows an attacker to run a playbook checklist task command as another user via creating and sharing a deceptive post action that unexpectedly runs a slash command in some arbitrary channel.

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 confidence

Mattermost fails to perform proper input validation on post actions in versions 9.5.x <= 9.5.3, 9.6.x <= 9.6.1, and 8.1.x <= 8.1.12. This allows authenticated attackers to craft deceptive post actions that execute playbook checklist task commands as another user in arbitrary channels, effectively enabling command injection through the post action mechanism.

MitigationUpgrade Mattermost to version 9.5.4, 9.6.2, 8.1.13 or later to receive the input validation fix for post actions.

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:>= 8.1.0, < 8.1.13>= 9.5.0, < 9.5.4>= 9.6.0, < 9.6.2

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

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/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 checks

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

  1. Identify Mattermost Server version
    Access the Mattermost System Console > About page, or run the command: mattermost version or check the /api/v4/system/stats endpoint
    Affected if The installed version falls within 8.1.0 to 8.1.12, 9.5.0 to 9.5.3, or 9.6.0 to 9.6.1 (i.e., version < 8.1.13, < 9.5.4, or < 9.6.2)
  2. Verify if Playbooks are enabled
    Navigate to Product menu > Playbooks, or check the playbooks plugin status via Mattermost CLI: mattermost plugin list
    Affected if The Playbooks/Automation feature is enabled and users have access to create or modify playbooks with checklist tasks
  3. Review audit logs for post action anomalies
    Check Mattermost audit logs (typically in /var/log/mattermost or via theAudits API at /api/v4/audits) for entries with action_type containing playbook task commands executed on posts in unexpected channels
    Affected if Audit logs show post action events where playbook checklist commands were executed by users in channels where they do not normally have permission to do so
  4. Inspect recent playbook run activity
    Use the Mattermost UI to review recent playbook runs and their checklist task executions, or query the database table named PlaybookRun to identify recent entries
    Affected if There are recent playbook runs where checklist task commands were triggered from posts in channels not associated with that playbook run

You are affected if your Mattermost Server version is 8.1.0-8.1.12, 9.5.0-9.5.3, or 9.6.0-9.6.1 AND the Playbooks feature 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 8.1.13 / 9.5.4 / 9.6.2 or later
Fixed in 8.1.139.5.49.6.2
Interim mitigation

Upgrade Mattermost to version 9.5.4, 9.6.2, 8.1.13 or later to receive the input validation fix for post actions.

Recommended fix High confidence

Mattermost Server 8.1.13, 9.5.4, or 9.6.2 (depending on current branch)

  1. Backup the Mattermost database and configuration files before upgrading
  2. Determine the currently installed Mattermost Server version via the system console or CLI
  3. For versions 8.1.0-8.1.12: Upgrade to Mattermost Server 8.1.13 or later
  4. For versions 9.5.0-9.5.3: Upgrade to Mattermost Server 9.5.4 or later
  5. For versions 9.6.0-9.6.1: Upgrade to Mattermost Server 9.6.2 or later
  6. After upgrade, verify the server is operational and test that post actions behave correctly
  7. Review system logs for any signs of exploitation attempts
Caveat Minor version upgrades typically do not introduce breaking changes, but review the Mattermost changelog for any configuration or feature changes between versions

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
  • Implementation3.0 h
  • Testing2.0 h
  • Review / QA1.0 h
8.0 hours of engineering $1,420
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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-2024-36255 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