CVE-2026-71958 in DWR-M961
Summary
by MITRE • 08/08/2026
D-Link DWR-M961 devices with hardware version C1 and software version 1.1.2_C1_202602110044 contain a buffer overflow vulnerability in the quicksetup.cgi interface. A remote attacker can write overly long strings to the test4, ssid2, and username fields and execute arbitrary commands by crafting a specific payload, or cause the device to crash.
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Analysis
by VulDB Data Team • 08/08/2026
The D-Link DWR-M961 router series represents a class of wireless broadband routers commonly deployed in residential and small office environments, with the specific hardware version C1 and software version 1.1.2_C1_202602110044 exhibiting a critical buffer overflow vulnerability within its web-based administration interface. This vulnerability resides in the quicksetup.cgi component which handles configuration parameters submitted through HTTP requests, making it accessible to remote attackers without authentication requirements. The flaw manifests when the application fails to properly validate input length for three specific parameters: test4, ssid2, and username fields, creating opportunities for malicious data injection that exceeds allocated buffer boundaries.
The technical implementation of this vulnerability stems from improper bounds checking within the web server's request processing logic, where user-supplied input is directly copied into fixed-length memory buffers without adequate sanitization or size validation. This classic buffer overflow condition occurs when an attacker crafts specially formatted HTTP requests containing excessively long strings in the vulnerable fields, causing stack corruption that can be exploited to overwrite adjacent memory locations including return addresses and function pointers. According to CWE-121, this represents a stack-based buffer overflow vulnerability that enables arbitrary code execution through strategic payload construction, while also aligning with ATT&CK technique T1203 for exploitation of software vulnerabilities to gain unauthorized access.
The operational impact of this vulnerability extends beyond simple denial-of-service conditions, as successful exploitation can provide attackers with complete control over the affected device, enabling persistent backdoor access, network reconnaissance, and potential lateral movement within compromised networks. Remote command execution capabilities allow threat actors to install malware, modify router configurations, redirect traffic through malicious proxies, or establish persistent access points for further attacks. The vulnerability's remote accessibility means that adversaries need only discover vulnerable devices on the internet to exploit them, with no local access requirements or privileged credentials needed for successful exploitation.
Mitigation strategies should prioritize immediate firmware updates from D-Link to address the identified buffer overflow conditions, though administrators must also implement network-level defenses including firewall rules that restrict access to port 80 and 443 on affected devices. Network segmentation and intrusion detection systems can help identify exploitation attempts through anomalous traffic patterns, while disabling unnecessary services and implementing strong authentication measures provides additional defense layers. The vulnerability demonstrates the critical importance of input validation in web applications and aligns with security best practices outlined in OWASP Top Ten and NIST SP 800-160 for secure software development lifecycle implementation. Organizations should conduct comprehensive vulnerability assessments to identify all affected D-Link devices within their network infrastructure and implement multi-layered security controls to protect against similar exploitation vectors.