CVE-2025-6370 is a critical security vulnerability identified in the D-Link DIR-619L router, specifically version 2.06B01. The flaw exists in the function formWlanGuestSetup located in the /goform/formWlanGuestSetup endpoint. The vulnerability arises due to improper handling of the 'curTime' argument, which leads to a stack-based buffer overflow. This type of overflow occurs when data exceeding the buffer's capacity is written to the stack, potentially overwriting adjacent memory and enabling arbitrary code execution or system crashes. The vulnerability is remotely exploitable without requiring user interaction or authentication, making it highly dangerous. The CVSS 4.0 base score is 8.7, indicating high severity, with attack vector being network (AV:N), low attack complexity (AC:L), no privileges required (PR:L), and no user interaction (UI:N). The impact on confidentiality, integrity, and availability is high (VC:H, VI:H, VA:H), meaning an attacker could fully compromise the device. Although the exploit has been publicly disclosed, there are no known exploits actively used in the wild at this time. Importantly, the affected product is no longer supported by D-Link, and no patches or updates are available, increasing the risk for users who continue to operate this device. The vulnerability affects only this specific firmware version, but given the device's deployment in home and small office environments, exploitation could lead to network compromise, data interception, or pivoting to other internal systems.

For European organizations, the impact of this vulnerability can be significant, especially for small and medium enterprises (SMEs) and home office setups that rely on the D-Link DIR-619L router for network connectivity. Exploitation could allow attackers to gain full control over the router, leading to interception of sensitive data, manipulation of network traffic, and potential lateral movement within the network. This could result in data breaches, disruption of business operations, and compromise of connected devices. Given the router's typical use in less hardened environments, attackers might exploit this vulnerability to establish persistent footholds or launch further attacks against corporate networks. Critical infrastructure or organizations with remote workers using this device may face increased risk. The lack of vendor support and patches exacerbates the threat, as affected organizations cannot remediate via official updates, increasing exposure time and the likelihood of exploitation once exploits become widespread.

Since the affected D-Link DIR-619L devices are no longer supported and no official patches exist, organizations must adopt alternative mitigation strategies. First, immediate replacement of the affected routers with currently supported and patched models is the most effective measure. If replacement is not immediately feasible, organizations should isolate these devices on segmented network zones with strict firewall rules to limit exposure to untrusted networks, especially the internet. Disabling remote management interfaces and restricting access to the /goform/formWlanGuestSetup endpoint can reduce attack surface. Network monitoring should be enhanced to detect anomalous traffic patterns indicative of exploitation attempts. Employing intrusion detection/prevention systems (IDS/IPS) with signatures targeting this vulnerability can help detect and block attacks. Additionally, organizations should conduct asset inventories to identify all instances of the DIR-619L and prioritize their decommissioning. User education about the risks of using unsupported devices and the importance of timely hardware upgrades is also critical. Finally, consider deploying network-level protections such as VPNs and strong authentication to reduce reliance on vulnerable edge devices.