CVE-2026-3715
Received Received - Intake
Stack-Based Buffer Overflow in Wavlink Firewall CGI Remote Exploit

Publication date: 2026-03-08

Last updated on: 2026-03-10

Assigner: VulDB

Description
A vulnerability was found in Wavlink WL-WN579X3-C 231124. This affects the function sub_40139C of the file /cgi-bin/firewall.cgi. Performing a manipulation of the argument del_flag results in stack-based buffer overflow. It is possible to initiate the attack remotely. The exploit has been made public and could be used. Upgrading to version 20260226 is able to mitigate this issue. You should upgrade the affected component. The vendor was contacted early, responded in a very professional manner and quickly released a fixed version of the affected product.
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Meta Information
Published
2026-03-08
Last Modified
2026-03-10
Generated
2026-06-16
AI Q&A
2026-03-08
EPSS Evaluated
2026-06-15
NVD
CVE-2026-3715
EUVD
EUVD-2026-10221
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
wavlink wl-wn579x3-c_firmware 231124
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-119 The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.
CWE-121 A stack-based buffer overflow condition is a condition where the buffer being overwritten is allocated on the stack (i.e., is a local variable or, rarely, a parameter to a function).
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Compliance Impact

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Impact Analysis

[{'type': 'paragraph', 'content': 'This vulnerability can have severe impacts on the affected device and its users. Because it allows remote exploitation without requiring local access or user interaction, an attacker can execute arbitrary code or cause the device to crash, leading to denial of service.'}, {'type': 'paragraph', 'content': "The compromise of the device's confidentiality, integrity, and availability means that sensitive data could be exposed or altered, and the device could be rendered unusable or controlled by an attacker."}, {'type': 'paragraph', 'content': 'Users of the affected router are strongly advised to upgrade to the fixed firmware version 20260226 to mitigate these risks.'}] [2, 3]

Executive Summary

[{'type': 'paragraph', 'content': 'CVE-2026-3715 is a stack-based buffer overflow vulnerability found in the Wavlink WL-WN579X3-C router, specifically in version 231124. The flaw exists in the function sub_40139C within the file /cgi-bin/firewall.cgi. It occurs when the argument "del_flag" is manipulated with crafted input, causing the function to write more data than a fixed-size stack buffer can hold due to the unsafe use of the sprintf function without bounds checking.'}, {'type': 'paragraph', 'content': 'An attacker can exploit this remotely by sending a specially crafted POST request to the router\'s firewall.cgi component with the "firewall" parameter set to "singlePortForwardDelete" and an excessively long "del_flag" value. This triggers the buffer overflow, which can lead to arbitrary code execution or denial of service on the affected device.'}] [1, 2, 3]

Detection Guidance

[{'type': 'paragraph', 'content': 'This vulnerability can be detected by sending a crafted POST request to the affected device\'s /cgi-bin/firewall.cgi endpoint. Specifically, the request should include the parameter "firewall" set to "singlePortForwardDelete" and an excessively long value for the "del_flag" argument to trigger the stack-based buffer overflow.'}, {'type': 'paragraph', 'content': 'A detection command example using curl could be:'}, {'type': 'list_item', 'content': 'curl -X POST http://<target-ip>/cgi-bin/firewall.cgi -d "firewall=singlePortForwardDelete&del_flag=$(python3 -c \'print("A"*200)\')"'}, {'type': 'paragraph', 'content': "This command sends a POST request with a long string of 'A's in the del_flag parameter to test if the device is vulnerable to the buffer overflow."}] [1, 3]

Mitigation Strategies

[{'type': 'paragraph', 'content': 'The immediate and recommended mitigation step is to upgrade the affected Wavlink WL-WN579X3-C device firmware to version 20260226 or later, which contains the fix for this vulnerability.'}, {'type': 'paragraph', 'content': "Until the upgrade can be applied, it is advisable to restrict remote access to the device's management interface to trusted networks only, to reduce the risk of exploitation."}, {'type': 'paragraph', 'content': "Downloading the fixed firmware is possible from the vendor's official site."}] [2, 4]

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