CVE-2017-18882
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 can occur via OpenGraph data.
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 confidenceThis is a stored Cross-Site Scripting (XSS) vulnerability in Mattermost Server where malicious scripts can be injected through OpenGraph metadata when links are shared in messages. OpenGraph data (used for link previews) is not properly sanitized before being rendered, allowing attackers to execute arbitrary JavaScript in victims' browsers.
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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Identify Mattermost Server installationCheck if Mattermost Server is running in your environment. Look for the mattermost process or check typical installation paths like /opt/mattermost or the Mattermost system console.Affected if Mattermost Server is not installed - not affected by this CVE.
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Determine the installed Mattermost versionAccess the Mattermost System Console > About or check the version via the mattermost server logs. Alternatively, run: grep -i 'version' /opt/mattermost/config/config.json or check the Mattermost version API endpoint if available.Affected if Installed version is < 4.1.2, OR >= 4.2.0 and < 4.2.1, OR exactly 4.3.0 - the environment is affected.
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Verify OpenGraph/link previews are enabledCheck the Mattermost config.json for the ServiceSettings.EnableLinkPreviews setting, or navigate to System Console > Posts > Enable Link Previews. This feature must be enabled for the XSS to be exploitable.Affected if Link previews are enabled on an affected version - the vulnerability can be exploited.
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Inspect OpenGraph metadata handling in logsReview Mattermost server logs for any unusual OpenGraph metadata patterns or warnings related to link preview processing. Check if custom OpenGraph parsers or third-party plugins are in use.Affected if Custom OpenGraph processing is in use without proper sanitization - potential indicator of exploitation.
The environment is affected if Mattermost Server is running a version in the ranges (< 4.1.2, >= 4.2.0 to < 4.2.1, or exactly 4.3.0) AND the link previews feature is enabled.
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 to patch the OpenGraph XSS vulnerability. If immediate upgrade is not possible, consider disabling link previews as a temporary mitigation.
- Consultation2.0 h
- Implementation2.0 h
- Testing3.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2017-18882 — 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-2017-18882 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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