CVE-2026-40615 in Totolink
Summary
by MITRE • 10/21/2026
A stack-based buffer overflow vulnerability exists in the boa formParentControl deviceName functionality of X2000R (version(s): TOTOLINK-X2000R-Gh-V1.0.0-B20250421.1327). A specially crafted HTTP request can lead to arbitrary code execution. An attacker can make an authenticated HTTP request to trigger this vulnerability.
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Analysis
by VulDB Data Team • 10/21/2026
The identified vulnerability represents a critical stack-based buffer overflow within the boa web server implementation of the TOTOLINK X2000R router, specifically affecting firmware version TOTOLINK-X2000R-Gh-V1.0.0-B20250421.1327 and potentially earlier or later builds sharing the same codebase. This flaw is located in the formParentControl deviceName functionality, which handles user input for parental control configurations. The underlying technical defect stems from a failure to properly validate the length of data provided by the client before copying it into a fixed-size buffer on the stack. When an attacker submits a specially crafted HTTP request containing a payload that exceeds the allocated memory space, the excess data overwrites adjacent memory locations, including critical return addresses and saved frame pointers. This corruption allows for precise control over the program counter, enabling the execution of arbitrary machine code within the context of the vulnerable process.
From a technical perspective, this vulnerability aligns with Common Weakness Enumeration identifier CWE-121, which describes stack-based buffer overflow conditions resulting from insufficient bounds checking on input data. The exploitation mechanism relies on the attacker crafting an HTTP POST request that targets the specific endpoint responsible for processing parental control device names. By injecting shellcode or a return-oriented programming sequence into the oversized payload, the attacker can hijack the execution flow of the boa server process. Since this functionality is accessible via standard web interfaces, the attack vector involves sending maliciously formatted requests to the router's management interface. The successful exploitation leads directly to arbitrary code execution with the privileges assigned to the web server daemon, which on many embedded devices often includes root-level access or significant system capabilities.
The operational impact of this vulnerability is severe, as it grants an authenticated attacker full control over the affected device. Once arbitrary code execution is achieved, the adversary can install persistent backdoors, exfiltrate sensitive network traffic, modify router configurations to facilitate further attacks on internal networks, or use the compromised device as a pivot point for lateral movement within the local area network. This compromises the confidentiality, integrity, and availability of both the host device and any connected systems relying on its routing services. The requirement for authentication does not mitigate the risk significantly in many real-world scenarios where default credentials are still prevalent, or where an attacker has already gained access through other means such as phishing or credential stuffing attacks.
Mitigation strategies should prioritize immediate firmware updates provided by TOTOLINK that address this buffer overflow issue. In cases where patching is not immediately feasible, network segmentation can help isolate the router from critical internal assets to limit lateral movement potential. Additionally, enforcing strong, unique administrative passwords reduces the likelihood of an attacker achieving the necessary authentication level required to trigger the vulnerability. Input validation and sanitization at the application layer are also recommended for developers maintaining similar embedded web interfaces to prevent stack-based overflows by ensuring all user-supplied data is strictly bounded before processing. Security monitoring tools should be configured to detect anomalous HTTP request patterns indicative of buffer overflow attempts, such as unusually long parameter values or malformed POST requests targeting configuration endpoints.