dbcve.org
Manageengine M365 Manager PlusApplication · Zohocorp

CVE-2021-42099

CRITICAL · 9.8 CVSS v3.1 Published 2021-11-30
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

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 · unedited
Zoho ManageEngine M365 Manager Plus before 4421 is vulnerable to file-upload remote code execution.

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 confidence

Zoho ManageEngine M365 Manager Plus versions before 4421 contain a file-upload vulnerability that allows unauthenticated attackers to upload malicious files and execute arbitrary code on the affected system.

MitigationUpgrade M365 Manager Plus to version 4421 or later. If immediate patching is not possible, restrict network access to the management interface and implement file upload validation controls at the network perimeter.

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
Manageengine M365 Manager PlusApplication
Affected:all versions= build_4000= build_4001= build_4002= build_4003= build_4004= build_4005= build_4007= build_4008= build_4009= build_4010= build_4011

CVSS 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 checks

Work through these to decide whether this CVE applies to you.

  1. Identify the installed build version
    Access the M365 Manager Plus administration interface and navigate to the About or System Information section to view the current build number. Alternatively, check the installation directory for a version file or check the service startup logs.
    Affected if The build number matches any of the listed affected builds (4000-4011) or is below 4421.
  2. Confirm the version number in application metadata
    Check the application's main executable or JAR file properties for the version metadata, or query the application's built-in API endpoint that returns version information if available.
    Affected if The version returned is earlier than 4421.
  3. Determine if the management interface is network-exposed
    Review network firewall rules and access control lists to determine whether the M365 Manager Plus web interface is accessible from untrusted networks or the internet.
    Affected if The management interface is reachable from untrusted networks without VPN or authentication barriers.
  4. Check for external file upload attempts
    Review web server access logs and application audit logs for suspicious upload requests to endpoints that handle file uploads, particularly those involving executable file types from unauthenticated sources.
    Affected if Unauthenticated upload requests to file upload endpoints are present in the logs.

You are affected if M365 Manager Plus is running a build version before 4421 and the management interface is network-accessible, allowing unauthenticated attackers to exploit the file upload vulnerability.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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 · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade M365 Manager Plus to version 4421 or later. If immediate patching is not possible, restrict network access to the management interface and implement file upload validation controls at the network perimeter.

Recommended fix High confidence

Version 4421 or later

  1. Back up the ManageEngine M365 Manager Plus installation and its configuration data
  2. Download the fixed version (4421 or later) from the official ManageEngine website
  3. Stop the M365 Manager Plus service before upgrading
  4. Install version 4421 or later following the vendor's official upgrade documentation
  5. Restart the M365 Manager Plus service after upgrade completion
  6. Verify the installation by logging into the admin console and confirming the version number
Caveat Review release notes for any configuration or feature changes between your current version and 4421

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Manageengine M365 Manager Plus Scoped from the published advisory
  • Consultation3.0 h
  • Implementation4.0 h
  • Testing4.0 h
  • Review / QA2.0 h
13.0 hours of engineering $2,280
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-42099 in production — separate from our analysis above.

No notes yet

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What this is

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.

What belongs here
  • 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