CVE-2017-20204 DBLTek GoIP Telnet Admin Interface Undocumented Backdoor
Remote attackers can bypass authentication on DBLTek GoIP devices via a flawed Telnet backdoor to gain root access and execute arbitrary code.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2017-20204?
CVE-2017-20204 is a critical authentication bypass vulnerability in DBL Technology (DBLTek) GoIP, published on 15 Oct 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-1242
Which versions are affected by CVE-2017-20204?
How do I fix CVE-2017-20204?
No fix has been published for CVE-2017-20204 yet. Limit exposure of the affected software until one is available.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2017-20204 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2017-20204 exists.
Sources
Also known as GHSA-5g7c-29rx-62p8.