# CVE-2021-35535: Insufficient Security Control Vulnerability

> An attacker with network access can exploit a boot sequence gap to load an older OS version, causing a denial of service on Hitachi Energy Relion devices.

- **Severity:** High 8.1 (`CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 18 Nov 2021
- **Updated:** 16 Sep 2024
- **Also known as:** GHSA-v26g-w7c2-rjj3

## What is CVE-2021-35535?

CVE-2021-35535 is a high-severity vulnerability in Hitachi Energy Relion 670 Series, published on 18 Nov 2021. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

Insecure Boot Image vulnerability in Hitachi Energy Relion Relion 670/650/SAM600-IO series allows an attacker who manages to get access to the front network port and to cause a reboot sequences of the device may exploit the vulnerability, where there is a tiny time gap during the booting process where an older version of VxWorks is loaded prior to application firmware booting, could exploit the vulnerability in the older version of VxWorks and cause a denial-of-service on the product. This issue affects: Hitachi Energy Relion 670 Series 2.2.2 all revisions; 2.2.3 versions prior to 2.2.3.3. Hitachi Energy Relion 670/650 Series 2.2.0 all revisions; 2.2.4 all revisions. Hitachi Energy Relion 670/650/SAM600-IO 2.2.1 all revisions.

Weakness: CWE-1188 (Initialization of a Resource with an Insecure Default)

## Which versions are affected by CVE-2021-35535?

It affects 3 products.


Products: Hitachienergy Relion 650 Firmware, Hitachienergy Relion 670 Firmware, Hitachienergy Relion Sam600-Io Firmware.

## How do I fix CVE-2021-35535?

No fix has been published for CVE-2021-35535 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-35535 being exploited?

There is no known exploitation of CVE-2021-35535 in the wild and no public exploit code.

## Other vulnerabilities in Hitachi Energy Relion 670 Series

- [CVE-2019-18247](https://insights.sbomify.com/CVE-2019-18247/): Denial of service in Relion 650 and 670 Series (high 7.5)
- [CVE-2023-4518](https://insights.sbomify.com/CVE-2023-4518/): Denial of service in Relion670 (medium 6.5)
- [CVE-2022-3864](https://insights.sbomify.com/CVE-2022-3864/): Security feature bypass in Relion 670/650/SAM600-IO Series (medium 4.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-35535 and fix it if it is affected.

What it is: CVE-2021-35535 is a high-severity vulnerability in Hitachi Energy Relion 670 Series, published on 18 Nov 2021. 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-2021-35535 in the wild and no public exploit code.

Affected product: Hitachi Energy Relion 670 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-2021-35535/ (Markdown: https://insights.sbomify.com/CVE-2021-35535/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-35535
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-35535
- OSV: https://osv.dev/vulnerability/CVE-2021-35535

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From sbomify Insights: https://insights.sbomify.com/CVE-2021-35535/
Summaries are generated and may contain mistakes; the official description above is the record.