CVE-2026-17539 Null dereference in RTU500 series CMU firmware
High-load IEC 104 requests trigger a NULL pointer dereference in Hitachi RTU500 firmware, causing connection restarts and denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-17539?
CVE-2026-17539 is a medium-severity vulnerability in Hitachi Energy RTU500 series CMU firmware, published on 3 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-476
Which versions are affected by CVE-2026-17539?
How do I fix CVE-2026-17539?
No fix has been published for CVE-2026-17539 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-17539 being exploited?
There is no known exploitation of CVE-2026-17539 in the wild and no public exploit code.
Sources
Also known as GHSA-9w2f-4f52-qcj4.