CVE-2020-4089
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 · uneditedHCL Notes is vulnerable to an information leakage vulnerability through its support for the 'mailto' protocol. This vulnerability could result in files from the user's filesystem or connected network filesystems being leaked to a third party. All versions of HCL Notes 9, 10 and 11 are affected.
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 confidenceHCL Notes contains a vulnerability in its mailto protocol handler that allows information disclosure. When a user clicks a specially crafted mailto link, the application can be tricked into exposing file paths or contents from the local filesystem or mounted network shares to a remote attacker.
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= 9.0= 10.0= 11.0CVSS 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
- Unchanged
- Confidentiality
- High
- Integrity
- None
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/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 HCL Notes installationLook for HCL Notes installation directory (commonly C:\Program Files\HCL\Notes or C:\Program Files (x86)\HCL\Notes), or check registry key HKLM\SOFTWARE\HCL\Notes or HKLM\SOFTWARE\Wow6432Node\HCL\Notes for InstallPath valueAffected if HCL Notes software is present on the system
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Identify installed HCL Notes versionCheck the Notes.exe executable version property (right-click Notes.exe in installation folder, select Properties, then Details), or query registry key HKLM\SOFTWARE\HCL\Notes\Version for the version stringAffected if Version is 9.0, 10.0, or 11.0 specifically
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Verify mailto protocol handler registrationCheck Windows registry under HKCR\mailto\shell\open\command (or HKLM\SOFTWARE\Classes\mailto\shell\open\command) to confirm Notes is registered as the handler for mailto: linksAffected if The registry shows HCL Notes executing mailto: links (the handler is active)
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Confirm user clickability of mailto linksAttempt to open a mailto: link in a web browser or document, or verify the Notes protocol handler is not disabled in Notes.ini (look for DisableMailto=1 setting)Affected if Mailto links are processed by HCL Notes and user interaction can trigger the handler
User is affected if HCL Notes versions 9.0, 10.0, or 11.0 is installed AND the mailto protocol handler is registered and enabled, allowing specially crafted mailto links to be processed.
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 dataApply vendor patches from HCL when available. Until then, users should avoid clicking mailto links from untrusted sources and administrators may consider disabling or sandboxing the mailto protocol handler in HCL Notes.
- Consultation2.0 h
- Implementation1.0 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-2020-4089 — 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-2020-4089 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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