# CVE-2026-21661: Johnson Controls CEM AC2000 privilege escalation via DLL hijacking

Source: https://junglewise.ai/threats/cve-2026-21661-johnson-controls-cem-ac2000  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-05-06. Updated: 2026-05-14  
License: CC BY 4.0 with a link back

CVE-2026-21661 · Severity: high · CVSS 8.7 · Published 2026-05-06

Johnson Controls CEM AC2000 is an access control and security management system used in critical infrastructure environments. A vulnerability in this software allows a user with low-level access to the host computer to gain full administrative control. This could lead to unauthorized access to sensitive security data, disruption of facility operations, or the ability to bypass physical security measures.

Vendors: [Johnson Controls](https://junglewise.ai/threats/vendors/johnson-controls).

## Quick answers

**Is CVE-2026-21661 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-21661 being exploited in the wild.

**How severe is CVE-2026-21661?** High severity, with a CVSS score of 8.7, published 6 May 2026.

**Which products and versions are affected?** Johnson Controls CEM AC2000 10.6, 11.0, 12.0.

**Is there a fix for CVE-2026-21661?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-21661 attacked?** It is attacked with local access, in an operating system.

**Am I affected by CVE-2026-21661?** Check whether you run Johnson Controls CEM AC2000 at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability is classified as an Uncontrolled Search Path Element (CWE-427), specifically manifesting as a DLL hijacking flaw. It resides in the CEM AC2000 software versions 10.6, 11.0, and 12.0. An attacker with local access and standard user privileges can place a malicious DLL in a location searched by the application, which is then executed with higher privileges. Successful exploitation allows for a full privilege escalation on the host machine. Johnson Controls has released updates (10.6 Release 3, 11.0 Release 9, and 12.0 Release 10) to remediate this issue.

## Affected products

- Johnson Controls Inc. CEM AC2000 10.6, 11.0, 12.0

## Timeline

- 2026-05-05: disclosed
- 2026-05-05: advisory

## References

- [https://www.cisa.gov/news-events/ics-advisories/icsa-26-125-05](https://www.cisa.gov/news-events/ics-advisories/icsa-26-125-05)