Security readout for executives and security teams
Plain-English summary
A local, low-privileged user could abuse how vulnerable Windows installations of AC2000 locate configuration files. Successful exploitation could seriously affect confidentiality and integrity, with limited availability impact. The issue is important but is not described as remotely exploitable.
Executive priority
Prioritize remediation in the near term, especially on systems allowing untrusted local access. The high impact warrants prompt upgrading, although available evidence does not support treating this as an active remote-exploitation emergency.
Technical view
CVE-2026-21661 is a CWE-427 uncontrolled search-path vulnerability. It affects AC2000 10.6 releases before 10, 11.0 releases before 9, and version 12 releases before 3. CVSS 4.0 scores it 8.4: local access and low privileges are required, but no user interaction is needed.
Likely exposure
Exposure is limited to AC2000 on Windows within the specified vulnerable release ranges. Exploitation requires local access with low privileges, reducing broad external exposure but increasing concern where users or processes have untrusted local access.
Exploitation context
The supplied record is not in CISA KEV and provides no evidence of active exploitation or a public exploit. It indicates configuration-file search paths can be leveraged or manipulated, but does not establish code execution, persistence, or a specific attack chain.
Researcher notes
The CVSS vector is AV:L/AC:L/AT:N/PR:L/UI:N with high vulnerable-system confidentiality and integrity impact. The bundle does not identify the affected executable, searched filename, writable directory, indicators, or exploitation outcome. Avoid assuming arbitrary code execution without additional vendor evidence.
Mitigation direction
- Upgrade AC2000 10.6 installations to release 10 or later.
- Upgrade AC2000 11.0 installations to release 9 or later.
- Upgrade AC2000 version 12 installations to release 3 or later.
- Restrict unnecessary local accounts and privileges until upgrades are completed.
- Check Johnson Controls guidance for deployment-specific remediation requirements.
Validation and detection
- Inventory AC2000 Windows hosts and record each installed version and release.
- Confirm no 10.6 installation is below release 10.
- Confirm no 11.0 installation is below release 9.
- Confirm no version 12 installation is below release 3.
- Review Johnson Controls advisories for updated detection guidance or indicators.
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-427: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. 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-2026-21661 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
- 8.4 (4.0)
- Known Exploited
- No
- Published
Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N
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.
SSVC decision data
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:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N——jciVulnerability scoring details
Base CVSS 4.0 score
8.4HighVector: CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- CVE publishedCVE Program
The CVE record was published.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
Source materials
- CVE List V5 sourceCVE List V5
- https://www.johnsoncontrols.com/trust-center/cybersecurity/security-advisoriesCVE reference, jci
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.
Uncontrolled Search Path Element
Uncontrolled Search Path Element represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.