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Mattermost ServerApplication · Mattermost

CVE-2023-5330

HIGH · 7.5 CVSS v3.1 Published 2023-10-09
Fix available
A fix is available. Upgrade to 7.8.11 / 8.0.3 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 enforce a limit for the size of the cache entry for OpenGraph data allowing an attacker to send a specially crafted request to the /api/v4/opengraph filling the cache and turning the server unavailable.

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 does not enforce a maximum size limit on OpenGraph cache entries. An attacker can send specially crafted requests to the /api/v4/opengraph endpoint that inflate cache entries beyond reasonable limits, exhausting server memory and causing denial of service.

MitigationImplement and enforce a maximum size limit for OpenGraph cache entries at both the application and cache configuration levels. Consider adding rate limiting on the /api/v4/opengraph endpoint to further reduce attack surface.

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:< 7.8.11>= 8.0.0, < 8.0.3>= 8.1.0, < 8.1.2

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
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 'grep -i version /opt/mattermost/version.go' or check the About section in the Mattermost System Console, or query the /api/v4/server/version endpoint
    Affected if The installed version falls within: < 7.8.11, >= 8.0.0 and < 8.0.3, or >= 8.1.0 and < 8.1.2
  2. Verify OpenGraph integration is enabled
    Check the Mattermost config.json file for 'EnableOpenGraph' setting under ServiceSettings, or navigate to System Console > Integration > Webhooks and Commands and verify 'Enable OpenGraph' is turned on
    Affected if OpenGraph is enabled (set to true) in the configuration
  3. Confirm external image proxy configuration
    Check config.json for 'EnableURLByOpenGraph' or the 'External Image Proxy' setting in System Console > Integration > CORS. This feature uses the /api/v4/opengraph endpoint when enabled.
    Affected if External image proxy or OpenGraph URL fetching is enabled and accessible to users
  4. Check for unusual memory usage patterns
    Monitor server memory consumption over time using 'top', 'htop', or the Mattermost Health Check endpoint. Look for spikes correlated with opengraph API calls.
    Affected if Memory usage grows abnormally and correlates with opengraph endpoint requests

You are affected if your Mattermost Server version is less than 7.8.11, between 8.0.0-8.0.3, or between 8.1.0-8.1.2 AND the OpenGraph feature is enabled, allowing unauthenticated or authenticated users to hit the /api/v4/opengraph endpoint.

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 7.8.11 / 8.0.3 / 8.1.2 or later
Fixed in 7.8.118.0.38.1.2
Interim mitigation

Implement and enforce a maximum size limit for OpenGraph cache entries at both the application and cache configuration levels. Consider adding rate limiting on the /api/v4/opengraph endpoint to further reduce attack surface.

Recommended fix High confidence

7.8.11 (for 7.x branch) or 8.0.3 (for 8.0.x) or 8.1.2 (for 8.1.x)

  1. Identify the current Mattermost Server version by checking the system console or running 'mattermost version'
  2. Determine the appropriate upgrade path based on current version: if < 7.8.11 upgrade to 7.8.11; if >= 8.0.0 and < 8.0.3 upgrade to 8.0.3; if >= 8.1.0 and < 8.1.2 upgrade to 8.1.2
  3. Before upgrading, perform a full backup of the database and configuration files
  4. Follow Mattermost upgrade documentation to upgrade to the specified fixed version (7.8.11, 8.0.3, or 8.1.2) or a later stable release
  5. After upgrade, verify the server is operational and the /api/v4/opengraph endpoint properly enforces cache size limits

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-2023-5330 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