CVE-2020-14458
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 · uneditedAn issue was discovered in Mattermost Server before 5.19.0. Attackers can discover private channels via the "get channel by name" API, aka MMSA-2020-0004.
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 confidenceThe 'get channel by name' API endpoint in Mattermost Server before version 5.19.0 lacks proper authorization checks, allowing unauthenticated or unauthorized attackers to enumerate and discover private channels that should be hidden from them. This information disclosure vulnerability enables reconnaissance of internal organizational structure.
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< 5.19.0CVSS 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
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- None
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/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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Check the installed Mattermost Server versionLog into the Mattermost server and run the command: `sudo mattermost version` or check the version through the system package manager (e.g., `dpkg -l mattermost-server` or `rpm -qi mattermost-server`). Alternatively, access the Mattermost System Console and navigate to the 'About' section to view the version.Affected if The installed version is lower than 5.19.0 (e.g., 5.18.x, 5.17.x, etc.).
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Verify if the 'get channel by name' API endpoint is accessibleAttempt to send an HTTP GET request to the API endpoint `GET /api/v4/teams/{team_id}/channels/name/{channel_name}` using a tool like `curl` or Postman, without providing valid authentication credentials or with a low-privilege user account.Affected if The API returns a successful response (HTTP 200) with channel details, including private channels, without requiring proper authorization (e.g., without a valid session token or with a token that lacks permission to access that channel).
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Confirm that private channels are being exposedUsing the API endpoint, request the name of a known private channel (e.g., a channel that is not listed in the public channels list) within a team. Check if the response includes sensitive information such as channel members, description, or other metadata that should be restricted.Affected if The API returns details of a private channel that the requesting user or unauthenticated request should not have access to, indicating that authorization checks are missing.
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Inspect the API security configurationCheck the Mattermost configuration file (config.json) for any settings related to API security, such as `ExtendSessionLengthWithActivity` or `SessionCache`, and ensure that the server is not running in a test or development mode that disables authorization checks.Affected if The configuration file shows non-default settings that disable authorization or authentication for the API (e.g., `DisableHTTPAPI` set to false, or `AllowCorsFrom` set to overly permissive values), but this is optional and may not be present in all deployments.
A defender is affected if the Mattermost Server version is below 5.19.0 and the 'get channel by name' API endpoint returns private channel details to unauthorized or unauthenticated users.
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 data5.19.0
Upgrade Mattermost Server to version 5.19.0 or later to resolve the improper authorization in the channel API. Verify that private channels are no longer accessible via this endpoint after patching.
- Consultation2.0 h
- Implementation4.0 h
- Testing3.0 h
- Review / QA2.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2020-14458 — 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-2020-14458 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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- Version or environment caveats, and links to real fixes
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