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Fencer Vulns
critical 9.3

CVE-2017-20204 json

DBLTek GoIP Telnet Admin Interface Undocumented Backdoor

published 2025-10-15 12 mo ago modified 2026-06-17 4 mo ago also EUVD-2017-18921

cvss
9.3
version 4.0, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.7%
EPSS 0.7% chance of exploitation in 30 days, percentile 53%
public exploits
0
none known

Summary

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

Exploitation
Proof of concept is public
Automatable
yes
Technical impact
total
Assessed
12 mo ago

Exploit prediction

0.69% chance of exploitation in the next 30 days, higher than 53% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • trustwave.com https://www.trustwave.com/en-us/resources/blogs/spiderlabs-blog/undocumented-backdoor-account-in-dbltek-goip/ referenced PoC, tagged "exploit" by a source, unverified
  • github.com https://github.com/JacobMisirian/DblTekGoIPPwn referenced PoC, tagged "exploit" by a source, unverified

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

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.