CVE-2026-110958 in WN530HG4B
Summary
by MITRE • 10/15/2026
A vulnerability was found in Wavlink WN530HG4B M30HG4B_V260724. The impacted element is an unknown function of the file api.cgi. The manipulation results in heap-based buffer overflow. It is possible to launch the attack remotely. The exploit has been made public and could be used. Upgrading to version 2026-09-24-841a51c6d5_tclinux.bin is sufficient to resolve this issue. The affected component should be upgraded. The vendor confirms: "We confirm the finding, and it has already been addressed. In the current firmware the api=info&client=app handler no longer builds a shell command: the login script is now invoked through an argument vector (execvp) instead of system(), and the client address is length-limited and null-checked."
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Analysis
by VulDB Data Team • 10/15/2026
The vulnerability identified in Wavlink WN530HG4B devices running firmware version M30HG4B_V260724 represents a critical security flaw within the device's web management interface. Specifically, the defect resides in an unknown function associated with the api.cgi script, which serves as a primary entry point for administrative interactions over HTTP. This component is particularly sensitive because it handles configuration and status queries that are often exposed to unauthenticated or low-privilege users on local networks. The core technical issue is classified as a heap-based buffer overflow, a severe memory corruption error where the application writes data beyond the allocated boundaries of a dynamically allocated memory block. Such vulnerabilities typically arise from improper validation of input lengths or failure to properly manage memory allocation during string manipulation operations within the CGI handler.
From an operational perspective, this flaw allows for remote code execution without requiring prior authentication in many IoT contexts, although specific exploitation details depend on the exact attack vector utilized by the attacker. The ability to launch attacks remotely significantly increases the risk profile of these devices, as they are often deployed in home or small office environments with limited network segmentation. An adversary can craft a malicious HTTP request containing an oversized payload designed to overwrite adjacent memory structures on the heap. By carefully controlling this overflow, it is possible to manipulate function pointers or return addresses stored within the process memory space. This manipulation enables the attacker to redirect program execution flow, ultimately leading to arbitrary code execution with the privileges of the compromised service account. The fact that public exploits exist for this vulnerability further exacerbates the threat landscape, making devices running vulnerable firmware highly susceptible to automated scanning and exploitation by malicious actors seeking to compromise IoT botnets or establish persistent backdoors within local networks.
The technical root cause is confirmed by the vendor as a result of unsafe command execution practices in earlier firmware versions. The original implementation utilized the system() function to build shell commands based on user-supplied input, specifically involving login scripts and client address parameters. This approach inherently risks injection attacks if inputs are not strictly sanitized, but more critically here, it contributed to memory management errors leading to heap corruption. In contrast, the remediated firmware version 2026-09-24-841a51c6d5_tclinux.bin addresses these issues through fundamental architectural changes in how commands are executed and validated. The updated handler no longer constructs shell command strings for execution; instead, it invokes login scripts using an argument vector via the execvp function. This method bypasses the shell interpreter entirely, preventing command injection attacks that rely on special characters like semicolons or pipes to chain malicious commands. Furthermore, the vendor has implemented strict length limitations and null-checks on client address inputs, ensuring that data processed by the application remains within expected bounds and does not trigger buffer overflows during memory allocation routines.
From a classification standpoint, this vulnerability aligns with CWE-120: Buffer Copy without Checking Size of Input (Classic Buffer Overflow) due to the heap-based nature of the flaw, as well as CWE-78: Improper Neutralization of Special Elements used in an OS Command if command injection vectors were also viable. In terms of adversary tactics, this vulnerability facilitates initial access and privilege escalation techniques documented under MITRE ATT&CK ID T1059 (Command and Scripting Interpreter) for the execution phase, while the exploitation method itself falls under T1203 (Exploitation for Client Execution). The transition from system() to execvp represents a best practice in secure coding standards such as OWASP Secure Coding Practices Guide, which advises against using shell interpreters when direct program invocation is sufficient.
To mitigate this risk immediately, administrators of Wavlink WN530HG4B devices must upgrade the firmware to version 2026-09-24-841a51c6d5_tclinux.bin or any later release that incorporates these security patches. It is crucial to verify the integrity of the downloaded firmware file before installation to prevent supply chain compromise during the update process. Beyond immediate patching, organizations should consider network-level mitigations such as isolating IoT devices in a separate VLAN with restricted access policies, ensuring that management interfaces are not exposed directly to untrusted networks like the public internet. Regular monitoring for unusual outbound traffic from these devices can also help detect potential exploitation attempts or subsequent lateral movement activities within the internal network infrastructure.