CVE-2017-20204

CVE-2017-20204 is a critical-severity vulnerability with a CVSS 4.0 base score of 9.3. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-1242.

Key facts

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.

Frequently asked questions

What is CVE-2017-20204?
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.
How severe is CVE-2017-20204?
CVE-2017-20204 has a CVSS 4.0 base score of 9.3, rated critical severity.
Is CVE-2017-20204 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (54th percentile), an estimate of the probability of exploitation in the next 30 days.
How do I fix CVE-2017-20204?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
Does CVE-2017-20204 have an EU (EUVD) identifier?
Yes. CVE-2017-20204 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2017-18921.
When was CVE-2017-20204 published?
CVE-2017-20204 was published on 2025-10-15 and last updated on 2026-06-17.

References

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