CVE-2017-18886
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 4.3.0, 4.2.1, and 4.1.2. It allows a bypass of restrictions on use of slash commands.
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 confidenceMattermost Server versions before 4.3.0, 4.2.1, and 4.1.2 contain a security flaw that allows authenticated users to bypass configured restrictions on slash command usage, potentially enabling unauthorized execution of restricted or disabled slash commands.
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< 4.1.2>= 4.2.0, < 4.2.1= 4.3.0CVSS 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
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/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 checksWork through these to decide whether this CVE applies to you.
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Identify installed Mattermost Server versionAccess the Mattermost System Console by navigating to the instance URL followed by /admin_console, then click 'About' in the main navigation, or use the mattermost server command line tool if available (e.g., mattermost version). Alternatively, check the /api/v4/system/ping endpoint which often returns version information in the response.Affected if The installed version falls within < 4.1.2, >= 4.2.0 and < 4.2.1, or equals 4.3.0
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Confirm slash command usage in the environmentNavigate to the Integrations section in the System Console ( Integrations > Slash Commands) and review the list of configured slash commands. Alternatively, use the mattermost command line tool to list integrations if available.Affected if One or more slash commands are configured in the system
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Identify restricted or disabled slash commandsIn the System Console under Integrations > Slash Commands, examine each command's configuration to identify any that have restrictions applied, are set to be disabled, or have specific usage limitations configured.Affected if Any slash commands have restrictions, disabled status, or usage limitations configured in the command settings
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Verify if bypass conditions could applyReview the execution behavior of restricted slash commands by attempting to invoke them with a standard authenticated user account that should NOT have permission, or review access logs for unexpected slash command executions that bypass configured restrictions.Affected if Users without proper permissions can successfully execute restricted or disabled slash commands, indicating the vulnerability is present
The environment is affected if Mattermost Server version is below 4.1.2, between 4.2.0 and 4.2.1 exclusive, or exactly 4.3.0, AND the system has slash commands with configured restrictions that could be bypassed.
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 data4.1.24.2.1
Upgrade Mattermost Server to version 4.3.0, 4.2.1, 4.1.2, or later. Prior to upgrading, document current slash command configurations to verify post-upgrade behavior matches expectations.
- Consultation2.0 h
- Implementation4.0 h
- Testing4.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2017-18886 — 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-2017-18886 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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