CVE-2020-14459
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 rename a channel and cause a collision with a direct message, aka MMSA-2020-0002.
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 confidenceIn Mattermost Server before version 5.19.0, an authorization flaw allows authenticated attackers to rename a channel to match the name of an existing direct message conversation. This creates a naming collision that can lead to unauthorized access or manipulation of direct message channels, likely due to improper validation of channel name uniqueness across different channel types.
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
- None
- Integrity
- High
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/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 checksWork through these to decide whether this CVE applies to you.
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Determine Mattermost Server versionRun 'mattermost version' from the server command line, or check the system console under About > Mattermost Version, or inspect the /opt/mattermost/version.txt fileAffected if The installed version is any version prior to 5.19.0 (e.g., 5.18.x, 5.17.x, etc.)
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Verify channel naming collision opportunityAs an authenticated user with channel management permissions, attempt to rename an existing public or private channel to match the name of an existing direct message conversation in the system. Use the channel settings to rename and observe if the operation completes without error.Affected if The server allows renaming a channel to duplicate the name of an existing direct message channel, indicating the uniqueness validation is missing
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Review audit logs for channel rename operationsAccess Mattermost Audit Logs (System Console > Audit Logs) and search for events where channel_name was modified. Look for multiple entries where channels were renamed to identical names across different channel types.Affected if Audit logs show channels renamed to names that already exist as direct message conversations, suggesting the vulnerability was exploited
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Check for unexpected direct message accessReview system logs and database records in the Channels table for entries where Type indicates DM (direct message) but the Name field matches that of a public/private channelAffected if Database contains channel name collisions between direct messages and regular channels, indicating the flaw exists or was exploited
A user is affected if their Mattermost Server version is below 5.19.0 AND the server permits renaming channels to duplicate existing direct message conversation names.
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 obtain the patch for this authorization bypass vulnerability.
- Consultation2.0 h
- Implementation4.0 h
- Testing6.0 h
- Review / QA2.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2020-14459 — 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-2020-14459 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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- 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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