| Title | TOTOLINK A720R V4.1.5cu.630_B20250509 Backdoor |
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| Description | A vulnerability has been identified in TOTOLINK A720R firmware within the cstecgi.cgi component. The firmware contains undocumented functionality that allows an attacker to enable the Telnet service by sending two specially crafted HTTP requests containing a hardcoded password and a validation code derived from the device's current date. The supplied values are verified by the firmware and, upon successful validation, the Telnet daemon is started through a call to `system()`.
Once enabled, the Telnet service can be accessed using the same hardcoded credentials, providing root-level access to the device. An unauthenticated attacker with network access to the management interface can therefore obtain full control over the affected device, compromising its confidentiality, integrity, and availability. |
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| Source | ⚠️ https://github.com/Xernary/a720r-telnet-backdoor |
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| User | Xernary (UID 91325) |
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| Submission | 06/15/2026 18:49 (1 month ago) |
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| Moderation | 07/27/2026 09:15 (1 month later) |
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| Status | Duplicate |
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| VulDB entry | 180225 [TOTOLINK A720R 4.1.5cu.470_B20200911 Telnet Service hard-coded credentials] |
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| Points | 0 |
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