GPL Odorizers GPL750

Summary

CISA disclosed CVE-2026-4436 in GPL Odorizers GPL750 gas odorant injection controllers (XL4, XL4 Prime, XL7, XL7 Prime), a high-severity (CVSS 8.6) missing authentication vulnerability affecting critical manufacturing infrastructure deployed worldwide. A low-privileged remote attacker can send Modbus packets to manipulate register values and cause incorrect odorant levels in gas lines. GPL Odorizers and Horner Automation provide firmware and software updates; no public exploitation has been reported.

Full text

ICS Advisory GPL Odorizers GPL750 Release DateApril 09, 2026 Alert CodeICSA-26-099-02 Related topics: Industrial Control System Vulnerabilities, Industrial Control Systems View CSAF Summary Successful exploitation of this vulnerability could allow a low privileged remote attacker to manipulate register values, which would result in too much or too little odorant being injected into a gas line. The following versions of GPL Odorizers GPL750 are affected: GPL750 (XL4) >=v1.0| GPL750 (XL4 Prime) >=v4.0| GPL750 (XL7) >=v13.0| GPL750 (XL7 Prime) >=v18.4| CVSS Vendor Equipment Vulnerabilities v3 8.6 GPL Odorizers GPL Odorizers GPL750 Missing Authentication for Critical Function Background Critical Infrastructure Sectors: Critical Manufacturing Countries/Areas Deployed: Worldwide Company Headquarters Location: United States Vulnerabilities Expand All + CVE-2026-4436 A low-privileged remote attacker can send Modbus packets to manipulate register values that are inputs to the odorant injection logic such that too much or too little odorant is injected into a gas line. View CVE Details Affected Products GPL Odorizers GPL750 Vendor:GPL Odorizers Product Version:GPL Odorizers GPL750 (XL4): >=v1.0|<v6.0, GPL Odorizers GPL750 (XL4 Prime): >=v4.0|<v6.0, GPL Odorizers GPL750 (XL7): >=v13.0|<v20.0, GPL Odorizers GPL750 (XL7 Prime): >=v18.4|<v20.0 Product Status:known_affected Remediations MitigationGPL Odorizers recommends users update to the latest software version of the GPL750 in connection with the latest firmware from Horner Automation for the XL4, XL4 Prime, XL7, and XL7 Prime devices.https://lincenergysystems-my.sharepoint.com/:f:/p/h_baer/IgDYaHIhXpyLQJvnKPd6b80TAUgV7Lp8qmVYBFUb0lmr7ak?e=JLeADm.https://lincenergysystems-my.sharepoint.com/:f:/p/h_baer/IgDYaHIhXpyLQJvnKPd6b80TAUgV7Lp8qmVYBFUb0lmr7ak?e=JLeADm MitigationGPL Odorizers recommends users clear the old files from their microSD cards, keeping only the LOGS folder and the FIRMWARE.LIC file if they have a WebMI license. The compressed folder downloaded from the link above can then be extracted to the root directory of the microSD card. These files already include the corresponding firmware update. If users do not have IT permissions to access their microSD cards, GPL Odorizers can provide preconfigured SD cards that technicians can simply swap into their odorizers prior to installation. MitigationFor assistance in updating GPL Odorizers to the latest version, users should reach out to GPL Odorizers directly via phone number (303) 697-6701 during the hours of 8:00 a.m. to 4:00 p.m. MST. MitigationHorner Automation offers firmware version 15.76 for their XL Series and version 17.30 for their XL Prime Series controllers https://hornerautomation.com/controller-firmware/. An installation guide is available for both the XL series and the XL Prime series.https://hornerautomation.com/controller-firmware/ Relevant CWE: CWE-306 Missing Authentication for Critical Function Metrics CVSS Version Base Score Base Severity Vector String 3.1 8.6 HIGH CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N Acknowledgments An anonymous researcher reported this vulnerability to CISA Legal Notice and Terms of Use This product is provided subject to this Notification (https://www.cisa.gov/notification) and this Privacy & Use policy (https://www.cisa.gov/privacy-policy). Recommended Practices CISA recommends users take defensive measures to minimize the risk of exploitation of this vulnerability. Minimize network exposure for all control system devices and/or systems, ensuring they are not accessible from the internet. Locate control system networks and remote devices behind firewalls and isolating them from business networks. When 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. CISA reminds organizations to perform proper impact analysis and risk assessment prior to deploying defensive measures. CISA 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. CISA encourages organizations to implement recommended cybersecurity strategies for proactive defense of ICS assets. Additional 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. Organizations observing suspected malicious activity should follow established internal procedures and report findings to CISA for tracking and correlation against other incidents. CISA also recommends users take the following measures to protect themselves from social engineering attacks: Do not click web links or open attachments in unsolicited email messages. Refer to Recognizing and Avoiding Email Scams for more information on avoiding email scams. Refer to Avoiding Social Engineering and Phishing Attacks for more information on social engineering attacks. No known public exploitation specifically targeting this vulnerability has been reported to CISA at this time. Revision History Initial Release Date: 2026-04-09 Date Revision Summary 2026-04-09 1 Initial Publication Legal Notice and Terms of Use This product is provided subject to this Notification and this Privacy & Use policy. Tags Sector: Critical Manufacturing Sector Topics: Industrial Control System Vulnerabilities, Industrial Control Systems Please share your thoughts We recently updated our anonymous product survey; we welcome your feedback. Related Advisories Apr 09, 2026 ICS Advisory | ICSA-26-099-01 Contemporary Controls BASC 20T Apr 07, 2026 ICS Advisory | ICSA-26-097-01 Mitsubishi Electric GENESIS64 and ICONICS Suite products Apr 02, 2026 ICS Advisory | ICSA-26-092-01 Siemens SICAM 8 Products Apr 02, 2026 ICS Advisory | ICSA-26-092-02 Yokogawa CENTUM VP

Indicators of Compromise

• cve — CVE-2026-4436

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