{"vulnerability": "CVE-2026-21661", "sightings": [{"uuid": "dc69412c-0ac2-41eb-9195-cfa2a49d9212", "vulnerability_lookup_origin": "1a89b78e-f703-45f3-bb86-59eb712668bd", "author": "9f56dd64-161d-43a6-b9c3-555944290a09", "vulnerability": "CVE-2026-21661", "type": "seen", "source": "https://www.cisa.gov/news-events/ics-advisories/icsa-26-125-05", "content": "View CSAF\n\nSummary\n\nSuccessful exploitation of this vulnerability could allow a standard user to escalate privileges on the host machine.\n\nThe following versions of Johnson Controls CEM AC2000 are affected:\n\n\n\nCEM AC2000 12.0 (CVE-2026-21661)\n\nCEM AC2000 11.0 (CVE-2026-21661)\n\nCEM AC2000 10.6 (CVE-2026-21661)\n\n<div class=\"csaf-table\">\n\n\n\n\nCVSS\nVendor\nEquipment\nVulnerabilities\n\n\n\n\nv3 8.7\nJohnson Controls Inc.\nJohnson Controls CEM AC2000\nUncontrolled Search Path Element\n\n\n\n</div>\n\nBackground\n\n\n\nCritical Infrastructure Sectors: Critical Manufacturing, Commercial Facilities, Government Services and Facilities, Transportation Systems, Energy\n\nCountries/Areas Deployed: Worldwide\n\nCompany Headquarters Location: Ireland\n\n\n\n\nVulnerabilities\n<div class=\"csaf-accordion\">\n\nExpand All +\n<div class=\"csaf-accordion-item\">\n\nCVE-2026-21661\n<div class=\"csaf-accordion-content\">\n\nThe affected product is vulnerable to DLL hijacking, which could allow an attacker to escalate standard user privileges on the host machine.\n\nView CVE Details\n\n\n\nAffected Products\n\nJohnson Controls CEM AC2000\n<div class=\"ics-vendor-version-status\">\n<div class=\"ics-vendor\">Vendor:Johnson Controls Inc.</div>\n<div class=\"ics-version\">Product Version:Johnson Controls Inc. CEM AC2000: 12.0, Johnson Controls Inc. CEM AC2000: 11.0, Johnson Controls Inc. CEM AC2000: 10.6</div>\n<div class=\"ics-status\">Product Status:known_affected</div>\n</div>\n<div class=\"ics-remediations\">\n\nRemediations\n\nMitigationJohnson Controls recommends users apply the following mitigations:\n\nMitigationUpgrade CEM AC 2000 12.0 to 12.0 Release 10.\n\nMitigationUpgrade CEM AC 2000 11.0 to 11.0 Release 9.\n\nMitigationUpgrade CEM AC 2000 10.6 to 10.6 Release 3.\n\nMitigationFor more detailed mitigation instructions, please see Johnson Controls Product Security Advisory.https://www.johnsoncontrols.com/trust-center/cybersecurity/security-advisories\n</div>\n\nRelevant CWE: CWE-427 Uncontrolled Search Path Element\n\n\n\nMetrics\n<div class=\"csaf-table csaf-metrics-table\">\n\n\n\n\nCVSS Version\nBase Score\nBase Severity\nVector String\n\n\n\n\n3.1\n8.7\nHIGH\nCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:L\n\n\n\n</div>\n</div>\n</div>\n</div>\n\n\n\nAcknowledgments\n\n\n\nTom Hulme of CSACyber reported this vulnerability to Johnson Controls\n\n\n\n\nLegal Notice and Terms of Use\n\nThis product is provided subject to this Notification (https://www.cisa.gov/notification) and this Privacy & Use policy (https://www.cisa.gov/privacy-policy).\n\n\n\nRecommended Practices\n\nCISA recommends users take defensive measures to minimize the risk of exploitation of this vulnerability.\n\nMinimize network exposure for all control system devices and/or systems, ensuring they are not accessible from the internet.\n\nLocate control system networks and remote devices behind firewalls and isolating them from business networks.\n\nWhen remote access is required, use more secure methods, such as Virtual Private Networks (VPNs), recognizing VPNs may have vulnerabilities and should be updated to the most current version available. Also recognize VPN is only as secure as the connected devices.\n\nCISA reminds organizations to perform proper impact analysis and risk assessment prior to deploying defensive measures.\n\nCISA also provides a section for control systems security recommended practices on the ICS webpage on cisa.gov/ics. Several CISA products detailing cyber defense best practices are available for reading and download, including Improving Industrial Control Systems Cybersecurity with Defense-in-Depth Strategies.\n\nCISA encourages organizations to implement recommended cybersecurity strategies for proactive defense of ICS assets.\n\nAdditional mitigation guidance and recommended practices are publicly available on the ICS webpage at cisa.gov/ics in the technical information paper, ICS-TIP-12-146-01B--Targeted Cyber Intrusion Detection and Mitigation Strategies.\n\nOrganizations observing suspected malicious activity should follow established internal procedures and report findings to CISA for tracking and correlation against other incidents.\n\nCISA also recommends users take the following measures to protect themselves from social engineering attacks:\n\nDo not click web links or open attachments in unsolicited email messages.\n\nRefer to Recognizing and Avoiding Email Scams for more information on avoiding email scams.\n\nRefer to Avoiding Social Engineering and Phishing Attacks for more information on social engineering attacks.\n\nNo known public exploitation specifically targeting this vulnerability has been reported to CISA at this time. This vulnerability is not exploitable remotely.\n\n\n\nRevision History\n\n\n\nInitial Release Date: 2026-05-05\n\n\n\n\n\nDate\nRevision\nSummary\n\n\n\n\n2026-05-05\n1\nInitial Republication of Johnson Controls product security advisory.\n\n\n\n\n\n\nLegal Notice and Terms of Use", "creation_timestamp": "2026-05-05T10:00:00.000000Z"}]}