CVE-2017-18880
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. XSS could occur via the title_link field of a Slack attachment.
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 confidenceA stored cross-site scripting (XSS) vulnerability exists in Mattermost Server versions prior to 4.3.0, 4.2.1, and 4.1.2. The vulnerability stems from insufficient sanitization of the title_link field within Slack attachments, allowing an attacker to inject malicious JavaScript that executes when other users view the attachment.
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
- None
- User interaction
- Required
- Scope
- Changed
- Confidentiality
- Low
- Integrity
- Low
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/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 Mattermost Server versionRun 'grep -i version /path/to/mattermost/config/config.json' or check the system console under About > Mattermost for the version numberAffected if The installed version is less than 4.1.2, OR between 4.2.0 and 4.2.1 (exclusive of 4.2.1), OR equal to 4.3.0
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Determine if Slack integration is enabledNavigate to System Console > Integrations > Slack and check if the 'Enable Slack import' or Slack webhook settings are enabled, or inspect the config.json for 'EnableSlackImport' or webhook settingsAffected if Slack integration is enabled and users can import or post Slack attachments
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Check for existing Slack attachments in postsSearch the database (SQL query: SELECT * FROM Posts WHERE type = 'slack_attachment' OR message LIKE '%attachments%') or review recent posts that may contain imported Slack contentAffected if Slack attachments exist in the system, particularly any with a title_link field populated
You are affected if your Mattermost Server version falls within the vulnerable range AND Slack integration is enabled or Slack attachments have been imported into channels.
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 or later (or to 4.2.1/4.1.2 as appropriate for each affected branch). Additionally, implement output encoding for the title_link field to prevent script execution.
- Consultation2.0 h
- Implementation4.0 h
- Testing2.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2017-18880 — 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-2017-18880 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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