CVE-2020-12670
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 · uneditedXSS exists in Webmin 1.941 and earlier affecting the Save function of the Read User Email Module / mailboxes Endpoint when attempting to save HTML emails. This module parses any output without sanitizing SCRIPT elements, as opposed to the View function, which sanitizes the input correctly. A malicious user can send any JavaScript payload into the message body and execute it if the user decides to save that email.
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 confidenceStored XSS vulnerability in Webmin's Read User Email Module (mailboxes endpoint). The Save function fails to sanitize SCRIPT elements when saving HTML emails, unlike the View function which properly sanitizes input. An attacker can inject malicious JavaScript payloads into email bodies that execute when recipients view the saved emails.
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<= 1.941CVSS 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 installed Webmin versionRun 'rpm -q webmin' or check the Webmin version via the Webmin UI at the bottom-left of any page, or look for /etc/webmin/version fileAffected if Version is 1.941 or lower (the mailboxes module is vulnerable in any version below 1.942)
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Confirm mailboxes module is enabledCheck if the mailboxes feature is listed in Webmin's available modules at Webmin > Webmin Configuration > Webmin Modules, or look for /usr/libexec/webmin/mailboxes/ directoryAffected if The mailboxes module exists and is installed - the vulnerability only applies if this module is present
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Verify save function accessibilityAttempt to access the mailboxes save endpoint or check user permissions for the mailboxes feature in Webmin under the Users > Email Mailboxes sectionAffected if Users with permission to save emails through the mailboxes interface can trigger the vulnerability; the flaw affects the Save function specifically, not View which sanitizes properly
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Inspect stored emails for suspicious contentUse the mailboxes interface to view saved emails, or check mail spool files in /var/spool/mail/ or the mailboxes data directory for HTML content containing script tagsAffected if Emails contain unsanitized HTML with script elements that would execute JavaScript when viewed in a browser
You are affected if Webmin version is 1.941 or lower AND the mailboxes module is enabled with users having save permissions, as the Save function does not sanitize script tags unlike the View function.
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 dataUpgrade Webmin to version 1.942 or later, which includes proper sanitization for the Save function. Until upgraded, restrict access to the mailboxes endpoint to trusted users only.
- Consultation2.0 h
- Implementation4.0 h
- Testing3.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2020-12670 — 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-2020-12670 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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