DBLTek GoIP Telnet Admin Interface Undocumented Backdoor

Published 12 mo ago 2025-10-15 · modified 4 mo ago 2026-06-17 · JSON

CVSS

9.3

v4.0 · CNA

CISA KEV

not known exploited

EPSS

0.7%

percentile 53%

Public exploits

none known

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.

CISA SSVC assessment

Exploitation: Proof of concept public
Automatable: yes
Technical impact: total
Assessed: 12 mo ago 2025-10-15

Exploit prediction (EPSS)

0.69% probability of exploitation in the next 30 days, higher than 53% of all scored CVEs.

CVSS scores

Assigned by	Version	Score	Vector
CNA	4.0	9.3	`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`
CNA	4.0	9.3	`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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X`

Affected products

DBL Technology (DBLTek) GoIP

Classification

Weakness

CWE-1242 Inclusion of Undocumented Features or Chicken Bits

References

dbltek.com / · product
trustwave.com /en-us/resources/blogs/spiderlabs-blog/undocumented-backdoor-account-in-dbltek-goip/ · technical-description, exploit
github.com /JacobMisirian/DblTekGoIPPwn · exploit
vulncheck.com /advisories/dbltek-goip-telnet-admin-interface-undocumented-backdoor · third-party-advisory

Sources

CVE List: CVE-2017-20204
NVD: CVE-2017-20204

vulnwire keeps one entry per vulnerability: the CVE id wins, then GHSA; records that alias each other are merged. Machine-readable: JSON.

Summary