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Mattermost ServerApplication · Mattermost

CVE-2025-9072

MEDIUM · 5.4 CVSS v3.1 Published 2025-09-15
Fix available
A fix is available. Upgrade to 10.5.10 / 10.9.5 or later.
See remediation →
58/100
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 10.10.x <= 10.10.1, 10.5.x <= 10.5.9, 10.9.x <= 10.9.4 fail to validate the redirect_to parameter, allowing an attacker to craft a malicious link that, once a user authenticates with their SAML provider, could post the user’s cookies to an attacker-controlled URL.

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

Open redirect vulnerability in Mattermost's SAML authentication flow where the redirect_to parameter is not validated, allowing attackers to craft malicious links that redirect authenticated users to attacker-controlled URLs after SAML login, potentially exfiltrating user cookies via POST requests.

MitigationApply vendor patches for affected versions (10.10.x > 10.10.1, 10.5.x > 10.5.9, 10.9.x > 10.9.4); implement strict allowlist validation for redirect_to parameter against trusted domains before use.

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:>= 10.5.0, < 10.5.10>= 10.9.0, < 10.9.5>= 10.10.0, < 10.10.2

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
Changed
Confidentiality
Low
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/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. Check installed Mattermost Server version
    Run 'mattermost version' or check the /opt/mattermost/version file. On Docker, run 'docker exec <container> mattermost version'. Compare the version number against the affected ranges: 10.5.0-10.5.9, 10.9.0-10.9.4, or 10.10.0-10.10.1
    Affected if The installed version falls within any of the affected ranges (10.5.x where x<10, 10.9.x where x<5, or 10.10.x where x<2)
  2. Verify SAML authentication is enabled
    Log into the Mattermost System Console, navigate to Authentication > SAML 2.0, or check the config.json file for 'SamlSettings': {'Enable': true}. On CLI, run 'mattermost config get SamlSettings'
    Affected if SAML authentication is enabled (the vulnerability only affects environments using SAML login)
  3. Confirm redirect_to validation is configured
    In System Console, navigate to Authentication > SAML 2.0 > Signup and look for 'redirect_to parameter validation' or 'allowed domains' settings. In config.json, check for any 'AllowedDomains' or similar validation fields under SAML settings. If these are missing or empty, the redirect_to parameter is not validated
    Affected if No allowlist of trusted domains is configured for the redirect_to parameter, or the validation is not functioning

You are affected if your Mattermost Server version is in the affected range AND SAML authentication is enabled AND no domain allowlist validation exists for the redirect_to parameter.

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 10.5.10 / 10.9.5 / 10.10.2 or later
Fixed in 10.5.1010.9.510.10.2
Interim mitigation

Apply vendor patches for affected versions (10.10.x > 10.10.1, 10.5.x > 10.5.9, 10.9.x > 10.9.4); implement strict allowlist validation for redirect_to parameter against trusted domains before use.

Recommended fix High confidence

10.10.2 (or 10.9.5/10.5.10 depending on your current branch)

  1. 1. Back up your Mattermost Server database and configuration files before proceeding
  2. 2. Determine your current Mattermost version by checking the system console or running mmctl version
  3. 3. Identify which version branch you are on (10.5.x, 10.9.x, or 10.10.x)
  4. 4. Download the appropriate fixed version: 10.10.2 for 10.10.x, 10.9.5 for 10.9.x, or 10.5.10 for 10.5.x
  5. 5. Stop the Mattermost Server service
  6. 6. Follow the official Mattermost upgrade documentation for your deployment method (deb/rpm package, Docker, or helm chart)
  7. 7. Install the upgraded package or container
  8. 8. Start the Mattermost Server service
Caveat Review Mattermost release notes for your target version to check for any breaking changes or required migration steps

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

Fix this in Mattermost Server Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA3.0 h
21.0 hours of engineering $3,680
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $5,888.

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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-2025-9072 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