# CVE-2021-36764: Null dereference in n/a

> Crafted communication requests cause a null pointer dereference in CODESYS Gateway, leading to a denial-of-service condition.

- **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:** 4 Aug 2021
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-qpw7-wx2f-6gc3

## What is CVE-2021-36764?

CVE-2021-36764 is a high-severity vulnerability in n/a, published on 4 Aug 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

In CODESYS Gateway V3 before 3.5.17.10, there is a NULL Pointer Dereference. Crafted communication requests may cause a Null pointer dereference in the affected CODESYS products and may result in a denial-of-service condition.

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2021-36764?

It affects 1 product.


Products: Codesys Gateway.

## How do I fix CVE-2021-36764?

No fix has been published for CVE-2021-36764 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-36764 being exploited?

There is no known exploitation of CVE-2021-36764 in the wild and no public exploit code.

## Other vulnerabilities in n/a

- [CVE-2022-31802](https://insights.sbomify.com/CVE-2022-31802/): Partial string comparison in CODESYS gateway server (critical 9.8)
- [CVE-2022-31804](https://insights.sbomify.com/CVE-2022-31804/): CODESYS Gateway server prone to denial of service attack due to excessive memory allocation (high 7.5)
- [CVE-2022-31803](https://insights.sbomify.com/CVE-2022-31803/): CODESYS Gateway Server V2 prone to Denial of Service Attack (medium 5.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-36764 and fix it if it is affected.

What it is: CVE-2021-36764 is a high-severity vulnerability in n/a, published on 4 Aug 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-2021-36764 in the wild and no public exploit code.

Affected product: n/a. 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-2021-36764/ (Markdown: https://insights.sbomify.com/CVE-2021-36764/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-36764
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-36764
- OSV: https://osv.dev/vulnerability/CVE-2021-36764

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-36764/
Summaries are generated and may contain mistakes; the official description above is the record.