CVE-2021-40377
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 · uneditedSmarterTools SmarterMail 16.x before build 7866 has stored XSS. The application fails to sanitize email content, thus allowing one to inject HTML and/or JavaScript into a page that will then be processed and stored by the application.
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 confidenceSmarterTools SmarterMail 16.x before build 7866 contains a stored XSS vulnerability where the application fails to sanitize email content, allowing attackers to inject malicious HTML and/or JavaScript that gets stored and executed when other users view the affected email content.
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>= 16.0.6345, < 16.3.7866CVSS 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
- Required
- Scope
- Changed
- Confidentiality
- Low
- Integrity
- Low
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:L/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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Verify SmarterMail installation and locate versionAccess the SmarterMail web admin interface (typically port 9998 or 443) and navigate to System > License & Registration, or check the Windows Services panel for the SmarterMail service and its associated version info.Affected if The application is not SmarterMail or no version information is available.
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Confirm the exact build numberIn the web admin interface, go to Help > About or System > Status to view the detailed build number (e.g., 16.0.XXXX or 16.3.XXXX).Affected if Unable to retrieve the build number from the admin interface.
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Compare build against affected rangeCompare your installed build number to the affected range: any version from 16.0.6345 up to but NOT including 16.3.7866 is vulnerable.Affected if Installed version falls within >= 16.0.6345 and < 16.3.7866.
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Verify email processing is enabledIn the admin interface, check that the email service (SMTP/IMAP/POP3) is enabled under Server > Services, or that users have the ability to receive and view emails.Affected if The email service is disabled or no users can receive/view email, making exploitation unlikely.
You are affected if SmarterMail build 16.0.6345 or higher is installed and email receiving/viewing is enabled, with the build being below 16.3.7866.
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 · scoped16.3.7866
Upgrade to SmarterMail build 7866 or later, which includes proper sanitization of email content. Until upgraded, implement input validation and output encoding for all email content processing.
16.3.7866 or later (Smartermail 16.x)
- Upgrade Smartermail from the current installed version (16.0.6345 or later but before 16.3.7866) to version 16.3.7866 or later
- After upgrade, verify the fix by testing that email content is properly sanitized and XSS payloads are not executed
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
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $5,888.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-40377 — 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-2021-40377 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
- No spam, self-promotion, credentials, or personal data