D-Link DI-8100 CVE-2026-7857

Requires valid high-privilege (administrator-level) credentials for the D-Link DI-8100 web management interface. The CVSS vector PR:H (High Privileges Required) confirms this authentication barrier. Exploitation targets the /user_group.asp CGI endpoint accessed via authenticated HTTP/HTTPS sessions. No special device configuration or non-default features are required beyond having the administrative web interface enabled, which is the default state for D-Link routers. Limiting factors that reduce widespread exploitation risk: (1) Admin credential requirement blocks unauthenticated mass scanning attacks. (2) Enterprise routers like DI-8100 typically have fewer exposed instances than consumer devices. (3) Attackers must chain this with credential compromise or social engineering to achieve initial access. However, once credentials are obtained, exploitation is straightforward - AV:N/AC:L indicates network-accessible attack with low complexity requiring no user interaction (UI:N) beyond initial authentication.

Real-world risk is MODERATE despite the 7.2 CVSS score. The CVSS vector (AV:N/AC:L/PR:H/UI:N) reveals network-accessible exploitation with low complexity but requires high privileges (administrator credentials). This significantly constrains opportunistic mass exploitation - attackers must first compromise admin credentials via phishing, credential stuffing, or exploiting another vulnerability. The E:P (Proof-of-concept) metric confirms public exploit code availability (GitHub repository linked in references), lowering technical barriers for attackers who have obtained credentials. No EPSS score or CISA KEV data provided, suggesting no confirmed widespread exploitation yet. However, enterprise routers are high-value targets for APT groups and ransomware operators seeking network persistence. The complete scope (C:H/I:H/A:H) means successful exploitation yields full device compromise - enabling network traffic interception, lateral movement, and persistent backdoor installation. Priority should be MEDIUM for organizations using DI-8100 in production, escalating to HIGH if internet-facing or if credential compromise is suspected. CRITICAL DATA GAP: Patch availability is not confirmed in provided data - vendor advisory URL (https://www.dlink.com/) lacks specifics. Organizations should verify current support status for firmware 16.07.26A1 before assuming fixes exist.

An attacker who has obtained D-Link DI-8100 administrator credentials (via phishing, credential reuse, or prior compromise) authenticates to the web management interface over the network. They craft a malicious HTTP request to /user_group.asp with oversized input parameters designed to overflow the sprintf buffer in the CGI handler. The buffer overflow overwrites adjacent memory including return addresses, redirecting execution to attacker-controlled shellcode that establishes a persistent backdoor on the router. Public exploit code on GitHub (https://github.com/draw-ctf/report/blob/main/DI-8100/user_group_asp_overflow.md) provides ready-made attack payloads, enabling even moderately skilled attackers to weaponize this vulnerability.