dbcve.org
MetasysApplication · Johnsoncontrols

CVE-2021-27657

HIGH · 8.8 CVSS v3.1 Published 2021-06-04
Fix available
A fix is available. Upgrade to after 11.0 or later.
See remediation →
94/100
Remediation priority · Urgent
Remotely reachable 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
Successful exploitation of this vulnerability could give an authenticated Metasys user an unintended level of access to the server file system, allowing them to access or modify system files by sending specifically crafted web messages to the Metasys system. This issue affects: Johnson Controls Metasys version 11.0 and prior versions.

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

This is an authenticated file system access vulnerability in Johnson Controls Metasys. An authenticated user can send specially crafted web messages to gain unauthorized access to the server file system, potentially allowing reading or modification of system files. The attack vector appears to be through the web interface/message handling subsystem of the Metasys application.

MitigationApply the vendor patch when available. Until then, limit Metasys user accounts to minimum necessary privileges, monitor for unusual file access patterns, and restrict network access to the Metasys server to trusted personnel only.

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
MetasysApplication
Affected:<= 11.0

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
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:L/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. Confirm Metasys web interface is exposed
    Identify if the Metasys web interface (typically accessed via browser on ports 80/443 or custom web ports) is reachable on your network. Check network firewall rules and internal access controls.
    Affected if The Metasys web interface is accessible to network users beyond trusted administrators.
  2. Identify the Metasys installation and version
    Locate the Metasys installation directory or access the Metasys system information through the administration console or registry (if on Windows). Look for version information in the application properties, About screen, or installation logs.
    Affected if The installed version is 11.0 or any earlier version (Metasys <= 11.0).
  3. Verify authentication is required for the web interface
    Confirm that the Metasys web interface enforces user authentication. Attempt to access the login page and determine if unauthenticated requests are rejected or redirected to a login form.
    Affected if The web interface accepts authenticated sessions, meaning a compromised or low-privilege account could potentially exploit this vulnerability.
  4. Review user account privileges
    Audit existing Metasys user accounts through the Metasys User Administrator tool. Identify accounts with elevated privileges and any accounts that may have been created recently or unexpectedly.
    Affected if Multiple authenticated users exist with access to the Metasys system, particularly those beyond the minimum required for operations.

Your environment is affected if Metasys version 11.0 or earlier is installed and its web interface is accessible to authenticated users on your network.

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
Upgrade available Upgrade to a release after 11.0
Interim mitigation

Apply the vendor patch when available. Until then, limit Metasys user accounts to minimum necessary privileges, monitor for unusual file access patterns, and restrict network access to the Metasys server to trusted personnel only.

Recommended fix High confidence

Metasys version 11.0.2 or later

  1. Identify the current Metasys version by accessing the Metasys system information or checking the About section in the Metasys UI
  2. Contact Johnson Controls technical support or visit the official Johnson Controls website to obtain Metasys version 11.0.2 or later
  3. Review the Metasys upgrade installation guide and release notes for version 11.0.2
  4. Schedule a maintenance window for the upgrade following organizational change management procedures
  5. Back up the current Metasys system database and configuration following standard backup procedures
  6. Install Metasys version 11.0.2 or later following the official installation documentation
  7. Verify the upgrade was successful by checking the Metasys version in the About section
  8. Validate that the vulnerability is patched by confirming the Metasys version is 11.0.2 or higher
Caveat Review release notes for any configuration changes or compatibility considerations before upgrading

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

Fix this in Metasys Scoped from the published advisory
  • Consultation3.0 h
  • Implementation6.0 h
  • Testing6.0 h
  • Review / QA3.0 h
18.0 hours of engineering $3,120
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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-2021-27657 in production — separate from our analysis above.

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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