CVE-2026-42025 in Totolink
Summary
by MITRE • 10/21/2026
Multiple exploitable stack-based buffer overflow vulnerabilities exist in the boa formIpv6Setup dhcp_dns 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 these vulnerabilities. This vulnerability concerns the dhcp_dns1 parameter.
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Analysis
by VulDB Data Team • 10/21/2026
The TOTOLINK X2000R router, specifically firmware version Gh-V1.0.0-B20250421.1327, contains critical security flaws within its web management interface that allow for remote code execution under specific conditions. The vulnerability resides in the boa formIpv6Setup dhcp_dns functionality, which is responsible for processing configuration parameters related to IPv6 DNS settings via DHCP. This component handles user input from HTTP requests and fails to perform adequate bounds checking on the data provided by the client before copying it into a fixed-size stack buffer. This lack of validation creates a classic stack-based buffer overflow condition where excessive input overwrites adjacent memory locations, including critical control flow data such as return addresses or function pointers stored on the call stack.
The technical nature of this flaw aligns with Common Weakness Enumeration (CWE) category CWE-121, which describes a stack-based buffer overflow resulting from insufficient boundary checks during local variable allocation and usage. When an attacker submits a specially crafted HTTP request containing a dhcp_dns parameter that exceeds the expected length limit, the application copies the entire string into the destination buffer without truncation or verification of its size relative to the allocated space. This overwrite corrupts the stack frame, allowing for precise manipulation of execution flow. By carefully crafting the payload to include shellcode and calculating appropriate return addresses, an attacker can hijack the program counter and execute arbitrary commands with the privileges of the vulnerable process, which typically runs with high-level administrative rights on embedded devices like routers.
From a threat actor perspective, this vulnerability is classified under MITRE ATT&CK technique T1059, specifically Command and Scripting Interpreter sub-techniques such as T1059.004 for Unix Shell or T1059.007 for JavaScript, depending on the payload constructed within the overflowed buffer. The requirement for authentication presents a significant barrier to opportunistic attacks but does not mitigate the severity of the flaw against authenticated adversaries. An attacker who has obtained valid credentials through phishing, credential stuffing, or other means can exploit this vulnerability directly over the network interface exposed by the router's web management service. This scenario is consistent with ATT&CK tactic T1078, Valid Accounts, where legitimate access privileges are abused to maintain persistence and escalate control within the network perimeter.
The operational impact of successfully exploiting these vulnerabilities extends far beyond simple device compromise. Since routers serve as gateways between internal networks and external internet connections, gaining code execution on this hardware allows an attacker to intercept, modify, or drop traffic traversing the network. This can facilitate man-in-the-middle attacks, DNS spoofing, and complete surveillance of unencrypted communications within the local area network. Furthermore, compromised IoT devices are frequently recruited into botnets for distributed denial-of-service (DDoS) attacks, turning a single router into a node in a larger malicious infrastructure. The ability to execute arbitrary code also enables attackers to install persistent backdoors or rootkits that survive reboots and standard security scans, leading to long-term unauthorized access.
Mitigation strategies must address both the immediate technical flaw and broader operational hygiene. For administrators currently running vulnerable firmware versions, the primary remediation is to upgrade to a patched version of the TOTOLINK X2000R firmware as soon as it becomes available from the vendor. Until an official patch is released, restricting access to the router's web management interface by disabling remote administration features and ensuring that administrative ports are not exposed to untrusted networks can reduce the attack surface. Additionally, implementing strict input validation at the application layer for all form parameters, particularly those handling DNS configurations, is essential to prevent buffer overflows in future software updates. Network segmentation should also be employed to limit lateral movement if a device is compromised, ensuring that critical assets remain isolated from potentially vulnerable IoT infrastructure.