# CVE-2026-8479: Null dereference in RTU500 series CMU firmware

> A specially crafted message sequence causes a null pointer dereference in RTU500 firmware, leading to denial of service when bidirectional IEC 60870-5-104 is enabled.

- **Severity:** Medium 6.9 (`CVSS:4.0/AV:A/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 26 May 2026
- **Updated:** 26 May 2026
- **Also known as:** GHSA-m2rr-g8pf-8wrj

## What is CVE-2026-8479?

CVE-2026-8479 is a medium-severity vulnerability in Hitachi Energy RTU500 series CMU firmware, published on 26 May 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

IEC 60870-5-104 used in bidirectional mode in RTU500 is vulnerable
for a NULL pointer dereferencing, if a specially crafted
sequence of messages is sent for a certain time, causing
Denial of Service impact.
Product is only affected if IEC 60870-5-104 functionality in
bidirectional mode (BCI) is configured.

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2026-8479?


## How do I fix CVE-2026-8479?

No fix has been published for CVE-2026-8479 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-8479 being exploited?

There is no known exploitation of CVE-2026-8479 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-8479 and fix it if it is affected.

What it is: CVE-2026-8479 is a medium-severity vulnerability in Hitachi Energy RTU500 series CMU firmware, published on 26 May 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-8479 in the wild and no public exploit code.

Affected product: Hitachi Energy RTU500 series CMU firmware. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-8479/ (Markdown: https://insights.sbomify.com/CVE-2026-8479/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-8479
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-8479
- OSV: https://osv.dev/vulnerability/CVE-2026-8479

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-8479/
Summaries are generated and may contain mistakes; the official description above is the record.