| Title | Wavlink NU516U1 V251208 Command Injection |
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| Description | # A remote command execution vulnerability exists in the `singlePortForwardDelete` function of the `firewall.cgi` component in the Wavlink NU516U1 (V251208) software.
### Overview
Supplier: Wavlink
Product: NU516U1 Version: WAVLINK-NU516U1-A-WO-20251208-BYFM
Type: command injection
### **Vulnerability description:**
A command injection vulnerability exists in the `/cgi-bin/firewall.cgi` component in Wavlink NU516U1 router firmware (version M16U1_V251208). The vulnerability is located in the **`sub_4016D0`** function that handles the **Port Forward Delete (singlePortForwardDelete)** functionality. When processing the `del_flag` parameter, the manufacturer calls the filter function `sub_405B2C` to check the user input. Although this function attempts to prevent command injection through a blacklist mechanism, its implementation is not rigorous and misses the key command delimiter semicolon (`;`). An authenticated remote attacker can bypass input validation by constructing a malicious **`del_flag`** parameter containing a semicolon, and use the `sprintf` function to splice arbitrary shell commands into a system call for execution, thereby taking full control of the device with root privileges. |
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| Source | ⚠️ https://github.com/Wlz1112/Wavlink-NU516U1-V251208-/blob/main/singlePortForwardDelete.md |
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| User | haimianbaobao (UID 94979) |
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| Submission | 02/03/2026 13:17 (4 months ago) |
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| Moderation | 02/17/2026 07:53 (14 days later) |
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| Status | Accepted |
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| VulDB entry | 346265 [Wavlink WL-NU516U1 up to 20251208 /cgi-bin/firewall.cgi singlePortForwardDelete del_flag command injection] |
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| Points | 20 |
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