# CVE-2021-35533: Specially Crafted IEC 60870-5-104 Packet Vulnerability in RTU500 series

> An attacker can cause a reboot of Hitachi Energy RTU500 CMU devices by sending a specially crafted IEC 60870-5-104 packet when the BCI function is enabled.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 26 Nov 2021
- **Updated:** 16 Sep 2024
- **Also known as:** GHSA-wv2v-prmm-j684

## What is CVE-2021-35533?

CVE-2021-35533 is a high-severity denial of service vulnerability in Hitachi Energy RTU500 series, published on 26 Nov 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Improper Input Validation vulnerability in the APDU parser in the Bidirectional Communication Interface (BCI) IEC 60870-5-104 function of Hitachi Energy RTU500 series allows an attacker to cause the receiving RTU500 CMU of which the BCI is enabled to reboot when receiving a specially crafted message. By default, BCI IEC 60870-5-104 function is disabled (not configured). This issue affects: Hitachi Energy RTU500 series CMU Firmware version 12.0.* (all versions); CMU Firmware version 12.2.* (all versions); CMU Firmware version 12.4.* (all versions).

Weakness: CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2021-35533?

It affects 1 product.


Products: Hitachienergy Rtu500 Firmware.

## How do I fix CVE-2021-35533?

No fix has been published for CVE-2021-35533 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-35533 being exploited?

There is no known exploitation of CVE-2021-35533 in the wild and no public exploit code.

## Other vulnerabilities in Hitachi Energy RTU500 series

- [CVE-2022-2502](https://insights.sbomify.com/CVE-2022-2502/): Denial of service in RTU500 series (high 7.5)
- [CVE-2022-4608](https://insights.sbomify.com/CVE-2022-4608/): Memory corruption in RTU500 series (high 7.5)
- [CVE-2023-6711](https://insights.sbomify.com/CVE-2023-6711/): Memory corruption in RTU500 series CMU Firmware (medium 5.9)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-35533 and fix it if it is affected.

What it is: CVE-2021-35533 is a high-severity denial of service vulnerability in Hitachi Energy RTU500 series, published on 26 Nov 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-35533 in the wild and no public exploit code.

Affected product: Hitachi Energy RTU500 series. 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-2021-35533/ (Markdown: https://insights.sbomify.com/CVE-2021-35533/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-35533
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-35533
- OSV: https://osv.dev/vulnerability/CVE-2021-35533

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-35533/
Summaries are generated and may contain mistakes; the official description above is the record.