# CVE-2021-21970: Memory corruption in Sealevel

> An out-of-bounds write in the SeaConnect 370W allows attackers to execute arbitrary code via crafted MQTT messages.

- **Severity:** Low 3.7 (`CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 4 Feb 2022
- **Updated:** 15 Apr 2025
- **Also known as:** GHSA-4prh-62v9-32q3

## What is CVE-2021-21970?

CVE-2021-21970 is a low-severity memory corruption vulnerability in Sealevel, published on 4 Feb 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 HandleSeaCloudMessage functionality of Sealevel Systems, Inc. SeaConnect 370W v1.3.34. The HandleIncomingSeaCloudMessage function uses at [3] the json_object_get_string to populate the p_name global variable. The p_name is only 0x80 bytes long, and the total MQTT message could be up to 0x201 bytes. Because the function json_object_get_string will fill str based on the length of the json’s value and not the actual str size, this would result in a possible out-of-bounds write.

Weakness: CWE-787 (Out-of-bounds Write), CWE-120 (Buffer Copy without Checking Size of Input)

## Which versions are affected by CVE-2021-21970?

It affects 1 product.


Products: Sealevel Seaconnect 370w Firmware.

## How do I fix CVE-2021-21970?

No fix has been published for CVE-2021-21970 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-21970 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-21970 exists.

## Other vulnerabilities in Sealevel

- [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-2021-21970 and fix it if it is affected.

What it is: CVE-2021-21970 is a low-severity memory corruption vulnerability in Sealevel, published on 4 Feb 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-2021-21970 exists.

Affected product: Sealevel. 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-2021-21970/ (Markdown: https://insights.sbomify.com/CVE-2021-21970/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-21970
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-21970
- OSV: https://osv.dev/vulnerability/CVE-2021-21970

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-21970/
Summaries are generated and may contain mistakes; the official description above is the record.