CVE-2021-20766
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 · uneditedCross-site scripting vulnerability in Message of Cybozu Garoon 4.0.0 to 5.0.2 allows a remote attacker to inject an arbitrary script via unspecified vectors.
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 confidenceCross-site scripting (XSS) vulnerability in Cybozu Garoon's message function allows remote attackers to inject arbitrary JavaScript code through unspecified vectors, potentially compromising session cookies or performing actions on behalf of authenticated users.
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>= 4.0.0, <= 5.0.2CVSS 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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Confirm Cybozu Garoon is installedAccess the application's system information page or check the product name in the web interface footer. Cybozu Garoon typically displays the product name on login pages and administrative screens.Affected if The application is not Cybozu Garoon (different product or not applicable).
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Determine the installed versionNavigate to the administration panel, typically found at /g/ or /portal/ and look for 'System Settings' or 'Version Information'. The version is often displayed in the system information or about section. Alternatively, check the garoon.ini configuration file if you have server access.Affected if Unable to determine the version - further investigation required.
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Compare version to affected rangeCheck if your installed version falls within >= 4.0.0 and <= 5.0.2. Versions 4.0.0 through 5.0.2 are affected. Versions below 4.0.0 or above 5.0.3 are not in the vulnerable range.Affected if Installed version is between 4.0.0 and 5.0.2 inclusive.
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Verify message function is accessibleLog in as a standard user and navigate to the message module (typically labeled 'Messages' or 'Mail' in the navigation). Confirm the function is enabled and accessible to users.Affected if Message function is disabled or not available to users - the XSS may not be exploitable in this configuration.
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Review message content for unexpected scriptsInspect messages in the inbox, sent items, or compose new message forms. Look for any message content containing <script> tags, javascript: URIs, or event handler attributes (onload, onerror, onclick, etc.) that were not intentionally created.Affected if Unexpected script tags or event handlers are found in message content.
If Cybozu Garoon version is between 4.0.0 and 5.0.2 and the message function is accessible, the environment is potentially affected by this XSS vulnerability.
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.
dbcve · scopedUpgrade Cybozu Garoon to version 5.0.3 or later which contains the security patch. Until then, implement input validation and output encoding on message handling functions as a compensating control.
Garoon 5.0.3 or later (latest stable 5.x release)
- 1. Back up your current Cybozu Garoon database and configuration files before any upgrade.
- 2. Review the release notes for Garoon versions newer than 5.0.2 to identify security fixes related to CVE-2021-20766.
- 3. Download the latest stable version of Garoon from the official Cybozu download portal (cs.cybozu.co.jp) or your licensed distribution channel.
- 4. Execute the upgrade installer following the standard Garoon upgrade procedure: stop the Garoon service, run the upgrade, then restart the service.
- 5. After upgrade, verify that the Message function works correctly and test that the XSS vulnerability is no longer present.
- 6. Clear browser cache and test with a non-privileged user account to confirm the fix.
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA3.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-20766 — 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-2021-20766 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
- No spam, self-promotion, credentials, or personal data