# CVE-2021-21967: Memory corruption in SeaConnect 370W

> An out-of-bounds write in the OTA update task allows a man-in-the-middle attacker to cause a denial of service via a crafted MQTT payload.

- **Severity:** Medium 6.5 (`CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/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:** 14 Apr 2022
- **Updated:** 15 Apr 2025
- **Also known as:** GHSA-8hfr-mj47-7cxj

## What is CVE-2021-21967?

CVE-2021-21967 is a medium-severity memory corruption vulnerability in Sealevel Systems, Inc. SeaConnect 370W, published on 14 Apr 2022. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

An out-of-bounds write vulnerability exists in the OTA update task functionality of Sealevel Systems, Inc. SeaConnect 370W v1.3.34. A specially-crafted MQTT payload can lead to denial of service. An attacker can perform a man-in-the-middle attack to trigger this vulnerability.

Weakness: CWE-120 (Buffer Copy without Checking Size of Input)

## Which versions are affected by CVE-2021-21967?

It affects 1 product.


Products: Sealevel Seaconnect 370w Firmware.

## How do I fix CVE-2021-21967?

No fix has been published for CVE-2021-21967 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-21967 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-21967 exists.

## Other vulnerabilities in Sealevel Systems, Inc. SeaConnect 370W

- [CVE-2021-21960](https://insights.sbomify.com/CVE-2021-21960/): Memory corruption in Sealevel (critical 10.0)
- [CVE-2021-21961](https://insights.sbomify.com/CVE-2021-21961/): Memory corruption in Sealevel (critical 10.0)
- [CVE-2021-21962](https://insights.sbomify.com/CVE-2021-21962/): Memory corruption in Sealevel (critical 9.0)
- [CVE-2021-21964](https://insights.sbomify.com/CVE-2021-21964/): Denial of service in Sealevel (high 8.6)
- [CVE-2021-21965](https://insights.sbomify.com/CVE-2021-21965/): Denial of service in Sealevel (high 8.6)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-21967 and fix it if it is affected.

What it is: CVE-2021-21967 is a medium-severity memory corruption vulnerability in Sealevel Systems, Inc. SeaConnect 370W, published on 14 Apr 2022. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-21967 exists.

Affected product: Sealevel Systems, Inc. SeaConnect 370W. 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-2021-21967/ (Markdown: https://insights.sbomify.com/CVE-2021-21967/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-21967
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-21967
- OSV: https://osv.dev/vulnerability/CVE-2021-21967

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-21967/
Summaries are generated and may contain mistakes; the official description above is the record.