CVE-2025-6291 is a critical security vulnerability identified in the D-Link DIR-825 router, specifically version 2.03. The flaw exists within the HTTP POST Request Handler component, in the function named do_file. This vulnerability is a stack-based buffer overflow, which occurs when an attacker sends specially crafted HTTP POST requests that manipulate the input to overflow the buffer on the stack. This overflow can corrupt adjacent memory, potentially allowing remote code execution or denial of service conditions. The vulnerability is remotely exploitable without requiring user interaction or authentication, making it highly dangerous. Although the affected product version is no longer supported by D-Link, the exploit code has been publicly disclosed, increasing the risk of exploitation by threat actors. The CVSS 4.0 score of 8.7 (high severity) reflects the vulnerability's ease of exploitation (network attack vector, low attack complexity, no privileges or user interaction required) and its significant impact on confidentiality, integrity, and availability. The vulnerability affects only the specific firmware version 2.03 of the DIR-825 model, which is a consumer and small office/home office (SOHO) router widely used for internet connectivity. No official patches or updates are currently available due to the product being out of support, which complicates mitigation efforts. The lack of known exploits in the wild at the time of publication does not diminish the threat, given the public availability of exploit details and the critical nature of the flaw.

For European organizations, the impact of this vulnerability can be substantial, especially for small and medium enterprises (SMEs) and home office setups that rely on the D-Link DIR-825 router for network connectivity. Successful exploitation could allow attackers to execute arbitrary code remotely, leading to full compromise of the router. This could enable attackers to intercept, modify, or redirect network traffic, launch man-in-the-middle attacks, or pivot into internal networks, severely compromising confidentiality and integrity of organizational data. Additionally, attackers could disrupt network availability by causing router crashes or persistent denial of service. Given the router’s role as a network gateway, exploitation could undermine perimeter security controls and facilitate further attacks on internal systems. The lack of vendor support and patches increases the risk of prolonged exposure. European organizations with limited IT security resources may find it challenging to detect and mitigate such attacks, increasing the likelihood of successful exploitation and potential data breaches or operational disruptions.

Since the affected D-Link DIR-825 version 2.03 is no longer supported and no official patches are available, organizations must adopt alternative mitigation strategies. First, immediate network segmentation should be implemented to isolate vulnerable routers from critical internal systems and sensitive data. Deploying network-level intrusion detection and prevention systems (IDS/IPS) with signatures or heuristics targeting HTTP POST anomalies can help detect exploitation attempts. Organizations should consider replacing the affected routers with currently supported models that receive security updates. If replacement is not immediately feasible, disabling remote management features and restricting HTTP POST access to trusted internal networks only can reduce exposure. Employing strict firewall rules to block unsolicited inbound traffic to the router’s management interface is essential. Regular network traffic monitoring and anomaly detection should be enhanced to identify suspicious activities indicative of exploitation attempts. Finally, educating users and administrators about the risks of using unsupported hardware and the importance of timely device replacement is critical to long-term security.