# CVE-2021-33823: Denial of service in n/a

> Attackers can exhaust web service resources via TCP SYN floods, causing denial of service on MOXA Mgate MB3180 devices.

- **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:** 18 Jun 2021
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-rwxq-4j33-72w4

## What is CVE-2021-33823?

CVE-2021-33823 is a high-severity denial of service vulnerability in n/a, published on 18 Jun 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

An issue was discovered on MOXA Mgate MB3180 Version 2.1 Build 18113012. Attacker could send a huge amount of TCP SYN packet to make web service's resource exhausted. Then the web server is denial-of-service.

## Which versions are affected by CVE-2021-33823?

It affects 1 product.


Products: Moxa Mgate Mb3180 Firmware.

## How do I fix CVE-2021-33823?

No fix has been published for CVE-2021-33823 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-33823 being exploited?

There is no known exploitation of CVE-2021-33823 in the wild and no public exploit code.

## Other vulnerabilities in n/a

- [CVE-2021-4161](https://insights.sbomify.com/CVE-2021-4161/): ICSA-21-357-01 Moxa MGate Protocol Gateways (critical 9.8)
- [CVE-2021-33824](https://insights.sbomify.com/CVE-2021-33824/): Denial of service in n/a (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-33823 and fix it if it is affected.

What it is: CVE-2021-33823 is a high-severity denial of service vulnerability in n/a, published on 18 Jun 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-2021-33823 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-2021-33823/ (Markdown: https://insights.sbomify.com/CVE-2021-33823/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-33823
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-33823
- OSV: https://osv.dev/vulnerability/CVE-2021-33823

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-33823/
Summaries are generated and may contain mistakes; the official description above is the record.