Hitachi Energy REB500
MonitorCVSS 6.5ICS-CERT ICSA-26-279-05Sep 29, 2026
Hitachi EnergyEnergy
Attack path
Attack VectorNetwork
Auth RequiredLow
ComplexityLow
User InteractionNone needed
Summary
Hitachi Energy REB500 protective relay devices versions 8.3.3.1 and earlier contain vulnerabilities in open-source software components that can be exploited to cause Denial of Service. An attacker with network access and valid credentials could exhaust device resources or trigger infinite loops, rendering the relay unresponsive to grid monitoring and protection functions.
What this means
What could happen
An attacker with network access and valid credentials could trigger a Denial of Service condition on the REB500, potentially disrupting protective relay operations and grid stability monitoring functions.
Who's at risk
Electric utilities and energy operators running Hitachi Energy REB500 protective relays (versions 8.3.3.1 and earlier). This device is commonly used for grid protection, feeder protection, and generator protection in substations and transmission systems.
How it could be exploited
An authenticated attacker with network access to the REB500 could exploit open-source software vulnerabilities in the device to send specially crafted traffic that causes resource exhaustion or infinite loops, making the relay unable to respond to grid conditions or trip commands.
Prerequisites
- Network access to REB500 management interface
- Valid user credentials for device access
- Knowledge of the vulnerable code paths in the product
remotely exploitableauthentication requireddenial of service impactaffects protective relay function
Exploitability
Some exploitation risk — EPSS score 1.4%
Public Proof-of-Concept (PoC) on GitHub (1 repository)
Affected products (1)
ProductAffected VersionsFix Status
REB500≤ 8.3.3.18.3.4.0
Remediation & Mitigation
0/1
Schedule — requires maintenance window
0/1Patching may require device reboot — plan for process interruption
HOTFIXUpdate REB500 firmware to version 8.3.4.0 or later
CVEs (2)
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