CVE-2026-91003 in DI-8300
Summary
by MITRE • 09/15/2026
A flaw has been found in D-Link DI-8300 16.07. The affected element is the function rzgl_asp of the file /rzgl.asp of the component CGI Service. This manipulation of the argument redirct_url causes stack-based buffer overflow. Remote exploitation of the attack is possible. The exploit has been published and may be used.
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Analysis
by VulDB Data Team • 09/15/2026
The vulnerability identified in D-Link DI-8300 firmware version 16.07 represents a critical security flaw within the device's Common Gateway Interface service, specifically located in the rzgl_asp function of the /rzgl.asp script. This component is responsible for handling web-based administrative requests and managing redirection logic for user sessions or configuration updates. The core technical issue stems from improper validation of input data passed to the redirct_url argument. When a remote attacker submits a specially crafted URL string that exceeds the expected buffer size, the application fails to perform adequate bounds checking before copying this data into a fixed-size stack memory location. This lack of sanitization results in a classic stack-based buffer overflow condition, where excess data overwrites adjacent memory regions on the call stack.
From an operational perspective, this vulnerability allows for remote code execution without requiring any form of authentication or user interaction beyond sending a malicious HTTP request to the target device's web interface. Because the flaw resides within a network-accessible CGI service that typically runs with elevated privileges necessary for router administration, successful exploitation can grant an attacker full control over the compromised system. The availability of public exploits significantly lowers the barrier to entry for threat actors, enabling widespread automated attacks against unpatched devices on the internet. This scenario aligns closely with CWE-120, which categorizes buffer copies without checking size limits as a fundamental memory safety error, and is further contextualized by MITRE ATT&CK technique T1190, describing exploitation of public-facing applications to gain initial access or execute arbitrary code within enterprise networks.
The impact of this vulnerability extends beyond simple device compromise. A successfully exploited router can be used as a pivot point for lateral movement within an internal network, facilitating data exfiltration, man-in-the-middle attacks against other connected devices, or participation in botnet activities such as distributed denial-of-service campaigns. The persistence of the flaw indicates that firmware updates may not have adequately addressed legacy code paths or that the vulnerability was introduced during a recent update cycle without sufficient regression testing for memory safety issues.
Mitigation strategies must prioritize immediate patching to the latest stable firmware version provided by D-Link, which should include fixes for input validation in CGI scripts. In environments where updating is not immediately feasible, network segmentation can help isolate vulnerable devices from critical internal resources. Additionally, deploying web application firewalls with rules designed to detect anomalous buffer overflow patterns or oversized URL parameters may provide a layer of defense against exploitation attempts. Long-term remediation requires developers to implement strict input validation and use memory-safe programming practices when handling user-supplied data in embedded systems to prevent similar stack-based overflows from recurring.