Security readout for executives and security teams
Plain-English summary
CVE-2021-27657 lets an authenticated Johnson Controls Metasys user gain unintended access to the server file system. In business terms, a low-privileged valid user could potentially view or alter system files on building management infrastructure running Metasys 11.0 or earlier.
Executive priority
Treat this as high priority where Metasys controls critical facilities, safety, or operational environments. It is not KEV-listed in the provided bundle, but the authenticated file-system impact can materially affect system integrity and availability.
Technical view
This is an improper privilege management issue in Johnson Controls Metasys 11.0 and prior. The CVSS 3.1 score is 8.8, with network access, low privileges, no user interaction, and high confidentiality, integrity, and availability impact.
Likely exposure
Organizations using Johnson Controls Metasys 11.0 or older are the stated exposure group. The source bundle does not identify affected CPEs, hosted configurations, or dependent modules, so asset inventory should confirm exact product version and deployment scope.
Exploitation context
The vulnerability requires an authenticated Metasys user and crafted web messages. CISA KEV status is false, and the provided sources do not state active exploitation, public exploit availability, or observed attacks.
Researcher notes
Evidence is limited to CVE metadata and advisory references. The bundle names the weakness, impact, affected version range, and CVSS vector, but does not provide patch details, detection indicators, or exploitation-in-the-wild evidence.
Mitigation direction
- Check Johnson Controls security advisories for the vendor-approved fix or upgrade path.
- Prioritize remediation for internet-reachable or broadly accessible Metasys servers.
- Limit Metasys access to trusted users and managed networks pending vendor remediation.
- Review file integrity and privileged access controls on affected servers.
- Do not assume a fixed version from this bundle; confirm with vendor guidance.
Validation and detection
- Inventory Metasys deployments and confirm whether version is 11.0 or earlier.
- Identify accounts with authenticated Metasys access and review privilege assignments.
- Check whether Metasys web access is exposed beyond required administrative networks.
- Review server logs for unusual authenticated web activity against Metasys.
- Assess criticality of building systems managed by affected servers.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-269: Authorization and privilege behavior lookup
Authorization weaknesses can support privilege escalation and valid-account review, depending on exploit path. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2021-27657 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- High
- CVSS
- 8.8 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H2.85.9Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
8.8HighVector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://www.johnsoncontrols.com/cyber-solutions/security-advisoriesCVE reference · x_refsource_CONFIRM
- ICS-CERT AdvisoryCVE reference · third-party-advisory, x_refsource_CERT
- ICS-CERT AdvisoryCVE reference · third-party-advisory, x_refsource_CERT
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Improper Privilege Management
Improper Privilege Management represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.