ABB System 800xA, Symphony Plus IEC 61850

Summary

ABB released a security advisory for CVE-2025-3756 affecting multiple IEC 61850 communication stack implementations in System 800xA, Symphony Plus, and related automation control products. The vulnerability allows attackers with network access to send specially crafted packets causing device faults or denial-of-service conditions in CI868, CI850, PM 877, and S+ Operations modules. Patches are planned for Q1–Q2 2026, with CVSS score 6.5 (Medium) and no active exploitation reported.

Full text

ICS Advisory ABB System 800xA, Symphony Plus IEC 61850 Release DateApril 30, 2026 Alert CodeICSA-26-120-01 Related topics: Industrial Control System Vulnerabilities, Industrial Control Systems View CSAF Summary This vulnerability was privately reported relating to ABB’s implementation of the IEC 61850 communication stack for MMS client applications used in some Automation control system products. Note: IEC 61850 communication typically supports MMS and GOOSE protocols. Some ABB products support both, others only MMS (e.g. S+ Operations and PM 877). In any case, GOOSE communication is not impacted by this reported vulnerability. If an attacker gains access to a site’s IEC 61850 network, then exploiting this vulnerability will result in a device fault (PM 877, CI850 and CI868 modules) and will require a manual restart. If this attack is directed at a S+ Operations node running IEC 61850 connectivity, this will result in a crash in the IEC 61850 communication driver which, if continued a repeating basis, will also result in a denial-of-service situation. Note that this does not have an impact on the overall availability and functionality of the S+ Operations node, only the IEC 61850 communication function. The System 800xA IEC61850 Connect is not affected. The following versions of ABB System 800xA, Symphony Plus IEC 61850 are affected: AC800M Product line (System 800xA) CI868 Symphony Plus SD Series CI850 Symphony Plus MR (Melody Rack) PM 877 S+ Operations Firmware <=6.0.0303.0, <=6.1.0031.0 , <=6.1.1004.0 , <=6.1.1202.0 , <=6.2.0006.0 , 6.1.1-3, 7.0, A_0, A_1, A_2.003, A_3.005, A_4.001, B_0.005, C_0, >=3.10|<=3.52, 3.53, 3.3, 2.3, 2.2, 2.1, 3.4 () CVSS Vendor Equipment Vulnerabilities v3 6.5 ABB ABB System 800xA, Symphony Plus IEC 61850 Improper Validation of Specified Quantity in Input Background Critical Infrastructure Sectors: Chemical, Critical Manufacturing, Energy, Water and Wastewater Countries/Areas Deployed: Worldwide Company Headquarters Location: Switzerland Vulnerabilities Expand All + CVE-2025-3756 A vulnerability exists in the command handling of the IEC 61850 communication stack included in the product revisions listed above. An attacker with access to IEC 61850 networks could exploit the vulnerability by using a specially crafted 61850 packet, forcing the communication interfaces of the PM 877, CI850 and CI868 modules into fault mode or causing unavailability of the S+ Operations 61850 connectivity, resulting in a denial-of-service situation. The System 800xA IEC61850 Connect is not affected. Note: This vulnerability does not impact on the overall availability and functionality of the S+ Operations node, only the 61850 communication function. View CVE Details Affected Products ABB System 800xA, Symphony Plus IEC 61850 Vendor:ABB Product Version: Product Status:fixed, known_affected Remediations Vendor fixABB advises all customers to review their installations to determine if they are using an impacted product as listed above, no further analysis or tools are needed to make this determination. The recommended immediate actions per product are listed below: - CI868 (for AC 800M) Devices with firmware versions reported in Affected products are vulnerable. All the vulnerabilities will be corrected in 6.1.1 and 7.0 tracks for 800xA. AC 800M 6.1.1-3 is planned for Q2 2027, AC 800M 7.0 has been released in December 2025. - CI850 (for Symphony Plus SD Series) Devices with firmware versions reported in Affected products are vulnerable. All the vulnerabilities will be corrected in version C_0 or later (planned Q2 2026). - PM 877 (Symphony Plus MR) Devices with firmware versions reported in Affected products are vulnerable. All the vulnerabilities will be corrected with firmware version 3.53 or later (planned Q1 2026). - S+ Operations Versions reported in Affected products are vulnerable. All the vulnerabilities will be corrected in version 3.4 or later (released in January 2026). ABB recommends customers apply updates, as they become available, at their earliest convenience. It is also advisable to review the Mitigating Factors, Workarounds and General security recommendations sections for additional actions which may help reduce overall risk. MitigationThe vulnerabilities announced in this Advisory for ABB Process Automation products require that an attacker has access to the system network and hosts which are generally expected to be protected. Process Control and IEC 61850 networks are NOT recommended to be exposed directly to Internet connections. If these networks are not properly isolated, then connected components may be remotely exploitable as described in this advisory. To exploit the vulnerability, an attacker with remote network access can send a specially crafted packet to the PM 877, CI850 and CI868 modules which causes the fault of these devices. S+ Operations only implements 61850 client services and therefore are not intended to listen to in-coming connection requests. However, if a specially crafted message is sent anyway, it can still cause the 61850-communication driver to crash. The usage of a perimeter firewall to allow legitimate client communications is an effective mitigation. Refer to section “General security recommendations” for further advise on how to keep your system secure. WorkaroundNo workarounds are available. Assess the installation specific risk based on this advisory. Use the recommendations described under “Mitigating factors” or “Recommended immediate actions”. Relevant CWE: CWE-1284 Improper Validation of Specified Quantity in Input Metrics CVSS Version Base Score Base Severity Vector String 3.1 6.5 MEDIUM CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Acknowledgments Hitachi Energy reported this vulnerability to ABB Global. ABB Global reported this vulnerability to CISA. Notice The information in this document is subject to change without notice, and should not be construed as a commitment by ABB. ABB provides no warranty, express or implied, including warranties of merchantability and fitness for a particular purpose, for the information contained in this document, and assumes no responsibility for any errors that may appear in this document. In no event shall ABB or any of its suppliers be liable for direct, indirect, special, incidental or consequential damages of any nature or kind arising from the use of this document, or from the use of any hardware or software described in this document, even if ABB or its suppliers have been advised of the possibility of such damages. This document and parts hereof must not be reproduced or copied without written permission from ABB, and the contents hereof must not be imparted to a third party nor used for any unauthorized purpose. All rights to registrations and trademarks reside with their respective owners. Frequently Asked Questions What is the scope of the vulnerability? - An attacker having access to the IEC 61850 network can force the ABB hardware devices to go to ‘fault’ state by sending a specially crafted 61850 packet. This will result in a denial-of-service situation affecting the primary functionality of the listed devices and requiring a manual reset. In the same way this vulnerability can cause the unavailability of the S+ Operations 61850 connectivity, if continued on a repeating basis (but not the whole S+ Operations node). The System 800xA IEC61850 Connect is not affected. What causes the vulnerability? - The vulnerability is caused by a weakness in the message processing in the IEC 61850 communication stack. What is CI868? - CI868 is a module used in AC800M product line (System 800xA) for IEC 61850 communication. What is CI850? - CI868 is a module used in Symphony Plus SD Series product line for IEC 61850 communication. What is PM 877? - PM 877 is a controller used in Symphony Plus MR (Melody Rack) product line for IEC 61850 communication. What is S+ Operations? - S+ Operations is the Human Machine Interface for supervision and control of Sympho

Indicators of Compromise

• cve — CVE-2025-3756

Entities