# Hitachi Energy GMS600 Vulnerable to OpenSSL Timing Attack—Critical Infrastructure at Risk


## The Threat


Hitachi Energy has disclosed a significant vulnerability in its GMS600 grid management system that leverages a timing-based side-channel flaw in OpenSSL's RSA implementation to potentially decrypt encrypted communications. CVE-2022-4304, originally identified in OpenSSL, enables attackers to recover the pre-master secret used in TLS handshakes through a Bleichenbacher-style attack—a sophisticated technique that exploits minute timing differences in cryptographic processing.


The vulnerability works by having an attacker send numerous trial messages to a targeted GMS600 server and measure the time each message takes to process. By analyzing these timing variations across thousands or millions of attempts, an attacker can gradually reconstruct the pre-master secret that was used to establish the original encrypted connection. Once recovered, this secret can be used to derive the session keys needed to decrypt all application data transmitted over that connection. This means attackers can potentially eavesdrop on communications that appeared to be protected by TLS encryption.


What makes this particularly concerning is that it affects critical infrastructure systems. The GMS600 is widely deployed in power grids and energy management environments globally. While a successful attack requires substantial computational resources and the ability to send a very large number of trial messages without being detected, the potential consequence—decryption of grid management communications—represents a genuine risk to infrastructure security and operational continuity.


## Severity and Impact


| Attribute | Details |

|-----------|---------|

| CVE ID | CVE-2022-4304 |

| CVSS v3.1 Base Score | 5.9 (MEDIUM) |

| Vector String | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N |

| Attack Vector | Network (AV:N) |

| Attack Complexity | High (AC:H) |

| Privileges Required | None (PR:N) |

| User Interaction | None (UI:N) |

| Scope | Unchanged (S:U) |

| Confidentiality Impact | High (C:H) |

| Integrity Impact | None (I:N) |

| Availability Impact | None (A:N) |

| Related CWE | CWE-203 (Observable Discrepancy) |

| Affected Component | OpenSSL (RSA Decryption) |


The MEDIUM severity rating reflects that while the confidentiality impact is high, the attack complexity is substantial. An attacker must send an enormous volume of specially crafted messages and perform significant analysis—work that might be detectable by network monitoring or rate limiting controls. However, the potential to decrypt confidential grid management traffic makes this a priority for operators in critical infrastructure sectors.


## Affected Products


Hitachi Energy GMS600:

  • Version 1.3.0
  • Version 1.3.1

    • These are the only versions confirmed affected by this vulnerability. Later versions and earlier releases should be reviewed against your deployment inventory to confirm your specific installation status.


    ## Mitigations


    Primary Remediation:

    Upgrade Hitachi Energy GMS600 to version 1.3.2 or later immediately. This version includes a patched version of OpenSSL that addresses CVE-2022-4304 in the RSA decryption implementation.


    Interim Workarounds (if immediate patching is not possible):

  • Implement strict ingress IP allowlisting to restrict which systems can communicate with GMS600 servers. Limit access to only authorized management stations and approved gateway systems.
  • Apply aggressive rate limiting on TLS connection attempts and message processing to make it prohibitively expensive for attackers to send the thousands of trial messages required for a successful attack.
  • Enforce network segmentation to isolate GMS600 systems from untrusted networks. Restrict east-west traffic and monitor for unusual communication patterns.
  • Monitor authentication logs and connection attempts for signs of brute-force or high-volume message flooding.
  • Consider temporarily shifting to out-of-band management channels if available, pending patch deployment.

    • Long-term Actions:

  • Maintain an inventory of all GMS600 deployments and their current versions.
  • Test version 1.3.2 in a staging environment before deploying to production.
  • Plan patch deployment windows with appropriate change control and stakeholder notification.

    • ## References


  • Hitachi Energy Security Advisory: https://www.hitachienergy.com/contact-us/
  • CVE-2022-4304 Details: https://nvd.nist.gov/vuln/detail/CVE-2022-4304
  • OpenSSL Security Advisory: https://www.openssl.org/
  • CISA Alert: https://www.cisa.gov/

    • ---


    ## HackWire Analysis


    This vulnerability highlights a persistent challenge in critical infrastructure security: the long tail of legacy systems running vulnerable components. OpenSSL CVE-2022-4304 was publicly disclosed in November 2022, yet more than two years later, Hitachi Energy is still issuing remediation guidance for GMS600 deployments stuck on vulnerable versions. This lag between disclosure and patching is endemic to industrial control systems, where operational uptime often outweighs security urgency.


    The Bleichenbacher timing attack itself is not new—the technique dates back to 1998—but its practical applicability depends heavily on network conditions and attacker capabilities. However, dismissing this as "too hard to exploit" would be a mistake. State-sponsored actors and sophisticated threat groups routinely invest in decryption of historical traffic. If an attacker has been recording GMS600 communications for months, they now have the theoretical ability to decrypt that entire archive. For utilities managing power distribution, water systems, or other critical infrastructure, the implications are serious.


    What's particularly notable is that this is *not* a vulnerability in GMS600 itself, but rather in a third-party component (OpenSSL) that Hitachi Energy integrated. This pattern—critical infrastructure relying on standard open-source cryptographic libraries with long vulnerability disclosure timelines—is widespread across the sector. Organizations deploying GMS600 should treat this as a case study: inventory all third-party components in critical systems, establish clear patch timelines, and maintain a dependency tracking process that can quickly identify when components require updates.


    The high attack complexity rating is accurate, but should not be read as "this won't happen." It should be read as "this is hard enough that it requires serious threat actors," which is precisely the category of adversary that critical infrastructure operators must assume will eventually target them.


    — HackWire Editorial


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