CVE-2026-7857 in DI-8100
Summary
by MITRE • 05/05/2026
A vulnerability has been found in D-Link DI-8100 16.07.26A1. This vulnerability affects the function sprintf of the file /user_group.asp of the component CGI Handler. The manipulation leads to buffer overflow. The attack may be initiated remotely. The exploit has been disclosed to the public and may be used.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 06/21/2026
The vulnerability in D-Link DI-8100 firmware version 16.07.26A1 represents a critical buffer overflow condition within the web interface's CGI handler component. This issue specifically targets the sprintf function implementation in the /user_group.asp file, which serves as a crucial interface for managing user access controls within the device's administration panel. The flaw exists in the manner in which user-supplied input is processed and formatted within the application's memory space, creating an exploitable condition that can be triggered through web-based interactions.
The technical nature of this vulnerability stems from improper input validation and memory management within the CGI handler module. When the sprintf function processes user-provided data without adequate bounds checking, it allows attackers to write data beyond the allocated memory buffer, potentially overwriting adjacent memory locations. This classic buffer overflow condition creates opportunities for arbitrary code execution and system compromise. The vulnerability's classification aligns with CWE-121, which describes stack-based buffer overflow conditions, and CWE-122, which covers heap-based buffer overflows, though the specific implementation suggests stack-based exploitation in this web context.
Remote exploitation of this vulnerability presents significant operational risks to networked environments, as attackers can initiate the attack through standard web browser interactions without requiring physical access to the device. The public disclosure of the exploit means that malicious actors can readily leverage this weakness, potentially gaining unauthorized administrative access to the router's management interface. This access could enable attackers to modify user groups, change administrative credentials, or even install malicious firmware, fundamentally compromising the security posture of networks relying on the affected device.
The impact extends beyond simple privilege escalation, as successful exploitation could provide attackers with persistent access to the network infrastructure. This vulnerability affects the core authentication and authorization mechanisms of the device, potentially allowing attackers to establish backdoors or maintain long-term access to the network. Network administrators should consider this vulnerability in the context of the MITRE ATT&CK framework, particularly under the T1078 technique for valid accounts and T1566 for spearphishing with a malicious attachment, as the compromised device could serve as a pivot point for further network infiltration. Organizations using this device should immediately implement mitigations including firmware updates, network segmentation, and monitoring for anomalous administrative access patterns.
The exploitation of this buffer overflow vulnerability demonstrates the importance of proper input sanitization and memory management in embedded web applications. The affected device's CGI handler component fails to implement adequate bounds checking mechanisms, allowing attackers to craft malicious input that exceeds the intended buffer capacity. This weakness highlights the need for comprehensive security testing of web interfaces in networked devices, particularly those handling user input through HTTP methods. The vulnerability's disclosure status means that automated scanning tools can identify affected devices, making prompt remediation essential for maintaining network security.