CVE-2023-2787
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 fails to check channel membership when accessing message threads, allowing an attacker to access arbitrary posts by using the message threads API.
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 versions prior to the fix contain an Insecure Direct Object Reference (IDOR) vulnerability in the message threads API. The API fails to validate that the requesting user is a member of the channel containing the target thread, allowing any authenticated user to read arbitrary posts by directly querying the threads API with known or guessed message IDs.
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>= 7.1.0, <= 7.1.9>= 7.8.0, <= 7.8.4>= 7.9.0, <= 7.9.3= 7.10.0CVSS 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
- High
- Integrity
- None
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/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 checksWork through these to decide whether this CVE applies to you.
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Determine installed Mattermost versionCheck the version through the Mattermost admin console (System Console > About) or by running 'mattermost version' from the command line if you have server accessAffected if The installed version falls within 7.1.0-7.1.9, 7.8.0-7.8.4, 7.9.0-7.9.3, or 7.10.0 exactly
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Verify API access is enabledConfirm that the REST API is accessible by checking the Mattermost configuration file (config.json) for 'EnableAPIv3' or by testing API endpoint accessibilityAffected if API v3 is enabled and accessible without additional restrictions
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Check thread API endpoint exposureTest access to the threads API endpoint (typically /api/v4/threads/{thread_id}) using an authenticated user account that is NOT a member of certain channelsAffected if The API returns thread content for channels the requesting user does not belong to, indicating the vulnerability is present
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Review user authentication configurationCheck if user authentication is required for API access by reviewing the 'EnableUserAccessToken' and 'EnableBotAccountCreation' settings in the System ConsoleAffected if Authenticated users exist in the system and can make API requests
You are affected if your Mattermost version is in the affected ranges AND the threads API returns posts from channels where the requesting user is not a member.
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.
From vendor dataApply the vendor patch which adds proper channel membership validation to the message threads API endpoint, ensuring users can only access threads from channels they belong to.
- Consultation2.0 h
- Implementation4.0 h
- Testing3.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,088.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2023-2787 — 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-2023-2787 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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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.
- 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
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