CISA published an advisory disclosing 14 vulnerabilities in Siemens Reyrolle 7SR5 protection relays, devices used in electrical substations worldwide to detect faults and trigger circuit breakers. The most severe, CVE-2026-62645, carries a CVSS score of 9.8 out of 10 and stems from the relay’s web interface exposing information that lets an attacker calculate current and past session IDs — enough to bypass authentication entirely without any privileges or user interaction.
The advisory also describes a related flaw allowing predictable session-ID generation from insufficient entropy, an out-of-bounds write reachable through crafted URLs that can force the device to reboot, and a physical-access vector that could allow unsigned code execution through a maintenance-mode key sequence. Siemens has released firmware version 2.70 to address the vulnerabilities; earlier versions remain exposed.
Why it matters
Protection relays are a core safety component of the electrical grid — an attacker who can bypass authentication on one gains the ability to interfere with fault detection and circuit-breaker operation, which is exactly the kind of access that grid-security planners worry about most.
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