CVE-2026-42021 in X2000R
Summary
by MITRE • 10/21/2026
Multiple stack-based buffer overflow vulnerabilities exist in the boa formIpv6Setup static network configuration functionality of Totolink X2000R 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 these vulnerabilities. This vulnerability concerns the static_dns1 parameter.
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Analysis
by VulDB Data Team • 10/21/2026
The Totolink X2000R router, specifically running firmware version TOTOLINK-X2000R-Gh-V1.0.0-B20250421.1327, contains critical security flaws within its web-based management interface that allow for remote code execution under specific conditions. These vulnerabilities are rooted in the handling of network configuration parameters via HTTP requests, particularly affecting the static_dns1 parameter used during IPv6 setup operations. The core issue lies in a stack-based buffer overflow condition present in the boa formIpv6Setup function, which is responsible for processing user-supplied input to configure DNS settings on the device. When an attacker provides a specially crafted string that exceeds the expected buffer size allocated by the application, it overwrites adjacent memory locations on the call stack, potentially altering control flow and allowing arbitrary code execution with the privileges of the web server process.
This vulnerability is classified under CWE-121, which describes stack-based buffer overflow conditions where input data is copied to a fixed-size buffer without adequate bounds checking. The operational impact is severe because it enables an authenticated attacker to gain full control over the router's operating system. Since the vulnerable function processes HTTP requests from the local network interface or potentially exposed management ports, exploitation requires initial authentication credentials. However, once authenticated, the attacker can inject malicious payloads that exploit the memory corruption to execute arbitrary commands on the device. This level of access allows for comprehensive compromise of the network infrastructure, including interception of traffic, modification of routing tables, and use of the router as a pivot point for further attacks against internal assets.
From an offensive security perspective, this vulnerability aligns with MITRE ATT&CK techniques related to initial access and execution on local devices. Specifically, it relates to T1059 Command Line Interface scripting or T1203 Exploitation for Client Execution if the payload is delivered via a browser-based exploit chain. The reliance on authenticated HTTP requests means that social engineering or credential theft may be prerequisites for exploitation in many real-world scenarios. Nevertheless, the presence of such high-severity flaws in embedded device firmware highlights significant deficiencies in secure coding practices during development and testing phases.
Mitigation strategies must focus primarily on immediate patching by updating to a version of the firmware where this buffer overflow has been remediated through proper input validation and bounds checking mechanisms. Administrators should ensure that administrative interfaces are not exposed to untrusted networks, utilizing VLAN segmentation or firewall rules to restrict access to management ports only from trusted IP ranges. Additionally, enforcing strong authentication policies and disabling unused services can reduce the attack surface. Until patches are applied, monitoring for anomalous HTTP requests containing unusually long strings in DNS configuration fields may help detect attempted exploitation activities.