Security readout for executives and security teams
Plain-English summary
This vulnerability affects Johnson Controls Facility Explorer SNC supervisory controllers. An authenticated user could gain broader file-system access than intended and read or change system files. For building operations, that can affect confidentiality, controller integrity, and potentially availability.
Executive priority
Treat as high priority for sites using affected Facility Explorer SNC controllers. The issue needs authenticated access, but impact spans file confidentiality, integrity, and availability on operational technology assets.
Technical view
CVE-2021-27661 is a CWE-269 privilege management issue in Facility Explorer SNC Series Supervisory Controllers. The CVSS 3.1 score is 8.8. Exploitation requires low privileges over the network, no user interaction, and specially crafted web messages to the F4-SNC.
Likely exposure
Organizations using Johnson Controls Facility Explorer SNC Series Supervisory Controllers, specifically the affected version listed in the CVE source bundle, are the relevant exposure group. Risk is higher where controller web access is reachable by many users or from broad networks.
Exploitation context
The sources describe authenticated exploitation only. The CVE is not marked as CISA KEV in the bundle, and no provided source states active exploitation. Evidence does not establish public exploit availability.
Researcher notes
The source bundle gives strong severity and affected-product evidence but limited remediation detail. Avoid assuming a patch level from the bundle alone. Validation should focus on asset/version confirmation, authenticated access paths, and vendor advisory status.
Mitigation direction
- Identify deployed Facility Explorer SNC F4-SNC controllers and versions.
- Check Johnson Controls and CISA advisory guidance for approved fixes or compensating controls.
- Restrict controller web access to trusted administration networks.
- Review and reduce user privileges on controller accounts.
- Monitor controller file-system integrity and authenticated web activity.
Validation and detection
- Confirm whether any F4-SNC controllers match the affected version in the source bundle.
- Verify who can authenticate to controller web interfaces.
- Review logs for unusual authenticated web requests or file changes.
- Confirm network segmentation limits controller access.
- Document whether vendor guidance has been reviewed and applied.
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-2021-27661 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
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.