| Title | Tenda A21 V1.0.0.0 Stack-based Buffer Overflow |
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| Description | During a security review of the Tenda A21 router firmware (version V1.0.0.0), a critical stack-based buffer overflow vulnerability was identified in the Wi-Fi configuration endpoint /goform/fast_setting_wifi_set.
The vulnerability exists within the form_fast_setting_wifi_set function. This function retrieves the user-controlled parameter ssid via the websGetVar interface and processes it into a fixed-size stack buffer ssid_5g (64 bytes). Due to the use of the unsafe sprintf function without length validation, an attacker can provide an overly long SSID to overwrite the stack, leading to a Denial of Service (DoS) or arbitrary code execution with root privileges. |
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| Source | ⚠️ https://github.com/QIU-DIE/cve-nneeww/issues/5 |
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| User | hhsw34 (UID 91076) |
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| Submission | 02/09/2026 12:46 (3 months ago) |
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| Moderation | 02/20/2026 15:41 (11 days later) |
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| Status | Accepted |
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| VulDB entry | 347111 [Tenda A21 1.0.0.0 fast_setting_wifi_set form_fast_setting_wifi_set ssid stack-based overflow] |
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| Points | 20 |
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