CVE-2021-3942
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 · uneditedCertain HP Print products and Digital Sending products may be vulnerable to potential remote code execution and buffer overflow with use of Link-Local Multicast Name Resolution or LLMNR.
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 confidenceA buffer overflow vulnerability exists in HP Print and Digital Sending products when Link-Local Multicast Name Resolution (LLMNR) is enabled. An unauthenticated remote attacker could exploit this buffer overflow to execute arbitrary code on affected devices due to improper handling of LLMNR network requests.
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>= 3.0, < 3.9.9>= 3.0, < 3.9.9>= 3.0, < 3.9.9>= 3.0, < 3.9.9>= 3.0, < 3.9.9>= 3.0, < 3.9.9>= 4.0, < 4.11.2.3>= 5.0, < 5.4>= 4.0, < 4.11.2.3>= 5.0.0, < 5.4CVSS 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
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
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 device model is affectedIdentify the exact product model number (CC419A, CC420A, CC421A, CE707A, CE708A, CE709A, 7ZU85A, or 7ZU86A) from the device label or management interfaceAffected if Model number matches one of the eight listed affected product numbers
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Check firmware version for Cm4540 or Cm5525 seriesAccess the printer web interface or control panel to view the installed firmware version. For CC419A, CC420A, CC421A, CE707A, CE708A, CE709A models, compare the version to the range >= 3.0 and < 3.9.9Affected if Firmware version is 3.0 or higher but below 3.9.9
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Check firmware version for M578 seriesAccess the printer web interface or control panel to view the installed firmware version. For 7ZU85A and 7ZU86A models, compare the version to the ranges >= 4.0 and < 4.11.2.3, OR >= 5.0.0 and < 5.4Affected if Firmware version is 4.0 or higher but below 4.11.2.3, OR 5.0.0 or higher but below 5.4
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Verify LLMNR is enabledAccess the printer network settings or web management interface and locate the LLMNR (Link-Local Multicast Name Resolution) setting. Check whether it is turned on or enabledAffected if LLMNR is currently enabled on the device
Device is affected if it is one of the eight listed HP Color LaserJet MFP models, runs a firmware version within the specified vulnerable ranges, AND has LLMNR enabled - all three conditions must be true.
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 · scoped3.9.94.11.2.35.4
Disable LLMNR on affected HP devices and apply vendor-supplied firmware updates when available. Additionally, network segmentation and firewall rules can limit exposure to LLMNR-based attacks from untrusted networks.
Firmware version 3.9.9 or later for Cm4540/Cm5525 series; Firmware version 4.11.2.3 or later OR 5.4 or later for M578 series
- 1. Identify the exact model number and current firmware version of the HP Laserjet MFP device
- 2. Navigate to HP Support (support.hp.com) and search for the specific product model
- 3. Locate the firmware download section for the device
- 4. Download the latest firmware version: for Cm4540/Cm5525 series - firmware version 3.9.9 or later; for M578 series - firmware version 4.11.2.3 or later, or version 5.4 or later for the 5.x branch
- 5. Follow HP's firmware update instructions, typically involving uploading the firmware file through the device's embedded web server (EWS) or HP Web Jetadmin
- 6. After update, verify the firmware version has been successfully upgraded
- 7. Consider disabling LLMNR in the device network settings as an additional mitigation if firmware update is not immediately possible
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $5,600.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-3942 — 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-2021-3942 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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- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
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