How severe is CVE-2026-21661?

CVE-2026-21661 has a CVSS 4.0 base score of 8.4, rated high severity.

Is CVE-2026-21661 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (1st percentile), an estimate of the probability of exploitation in the next 30 days.

How do I fix CVE-2026-21661?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2026-21661 have an EU (EUVD) identifier?

Yes. CVE-2026-21661 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-27865.

When was CVE-2026-21661 published?

CVE-2026-21661 was published on 2026-05-06 and last updated on 2026-06-17.

CVE-2026-21661

CVE-2026-21661 is a high-severity vulnerability with a CVSS 4.0 base score of 8.4. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-427.

Key facts

Severity: High (CVSS 4.0 base score 8.4)
EPSS exploit prediction: 0% (1st percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-27865
Weakness: CWE-427
Published: 2026-05-06
Last modified: 2026-06-17

Description

Uncontrolled Search Path Element vulnerability in JohnsonControls AC2000 on Windows allows Leveraging/Manipulating Configuration File Search Paths. This issue affects AC2000: from 10.6 before release 10, from 11.0 before release 9, from 12 before release 3.

Frequently asked questions

What is CVE-2026-21661?: Uncontrolled Search Path Element vulnerability in JohnsonControls AC2000 on Windows allows Leveraging/Manipulating Configuration File Search Paths. This issue affects AC2000: from 10.6 before release 10, from 11.0 before release 9, from 12 before release 3.
How severe is CVE-2026-21661?: CVE-2026-21661 has a CVSS 4.0 base score of 8.4, rated high severity.
Is CVE-2026-21661 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (1st percentile), an estimate of the probability of exploitation in the next 30 days.
How do I fix CVE-2026-21661?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2026-21661 have an EU (EUVD) identifier?: Yes. CVE-2026-21661 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-27865.
When was CVE-2026-21661 published?: CVE-2026-21661 was published on 2026-05-06 and last updated on 2026-06-17.

References

https://www.johnsoncontrols.com/trust-center/cybersecurity/security-advisories

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