ABB legacy KNX devices lack firmware integrity check

A missing firmware integrity check in ABB's legacy KNX Update Tool lets an attacker with physical bus access tamper with device firmware, and ABB has no plans to fix it.

CISA republished an ABB PSIRT advisory describing CVE-2026-12705, a missing firmware image integrity check (CWE-353) affecting the ABB and Busch-Jaeger (BJE) KNX Update Tool versions 2.0.175 and earlier. The flaw impacts only classic/legacy KNX devices that do not support the newer KNX Data Secure standard introduced in 2017; because these legacy devices lack the underlying security architecture needed, ABB states the issue cannot be resolved with a software update and has no corrective measures planned.

Exploitation requires physical access to the KNX bus the target device is connected to — there is no remote attack vector. An attacker with such access could tamper with or intercept the firmware image during an update, potentially causing the device to malfunction or, if capable of reverse engineering the firmware, altering device behavior. ABB recommends general security guidelines and specifically advises against using legacy KNX devices for sensitive functions such as access control (e.g., hotel room locks). The vulnerability was responsibly disclosed by academic researchers from Southeast University, University of Massachusetts Lowell, and Shandong University, and there is no evidence of in-the-wild exploitation. Given the requirement for physical bus access and absence of active exploitation, this is a low-urgency but persistent architectural weakness in widely deployed building automation hardware.

Source reporting: https://www.cisa.gov/news-events/ics-advisories/icsa-26-209-07