CVE-2025-7911 is a critical stack-based buffer overflow vulnerability identified in the D-Link DI-8100 router, specifically affecting version 1.0 of the device's firmware. The vulnerability resides in the handling of the 'sprintf' function within the /upnp_ctrl.asp file of the jhttpd component, which is responsible for processing HTTP requests related to UPnP control. The flaw is triggered by manipulating the 'remove_ext_proto' and 'remove_ext_port' arguments, leading to a stack-based buffer overflow condition. This overflow can be exploited remotely without authentication or user interaction, allowing an attacker to potentially execute arbitrary code on the device with elevated privileges. The vulnerability has a CVSS 4.0 base score of 8.7, indicating high severity, with attack vector being network-based (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, as successful exploitation could lead to full device compromise, enabling attackers to manipulate network traffic, intercept data, or disrupt network services. Although no known exploits are currently observed in the wild, the public disclosure of the exploit code increases the risk of imminent attacks. The vulnerability affects a widely deployed consumer and small business router model, which is often used in home and office environments, making it a significant threat vector for network perimeter security.

For European organizations, the exploitation of CVE-2025-7911 could have severe consequences. Many small and medium enterprises (SMEs) and home offices across Europe rely on D-Link DI-8100 routers for internet connectivity and network management. A successful attack could lead to unauthorized access to internal networks, interception of sensitive communications, and potential lateral movement to other critical systems. This could result in data breaches involving personal data protected under GDPR, leading to regulatory fines and reputational damage. Additionally, compromised routers could be leveraged as entry points for broader cyber espionage or ransomware campaigns targeting European businesses. The disruption of network availability could also impact operational continuity, especially for organizations with remote work setups dependent on stable internet connections. Given the remote exploitability and lack of required user interaction, the threat is particularly acute in environments where patch management is delayed or where legacy devices remain in use.

To mitigate the risk posed by CVE-2025-7911, European organizations should take immediate and specific actions beyond generic advice: 1) Identify and inventory all D-Link DI-8100 devices within the network, including those in remote or branch offices. 2) Check for and apply any official firmware updates or patches released by D-Link addressing this vulnerability; if no patch is currently available, contact D-Link support for guidance or consider device replacement. 3) Implement network segmentation to isolate vulnerable devices from critical infrastructure and sensitive data repositories. 4) Restrict access to router management interfaces by limiting exposure to internal networks only and employing strong access controls such as IP whitelisting and multi-factor authentication where possible. 5) Monitor network traffic for unusual patterns indicative of exploitation attempts, such as malformed UPnP requests targeting /upnp_ctrl.asp. 6) Deploy intrusion detection/prevention systems with updated signatures to detect exploitation attempts. 7) Educate IT staff about the vulnerability and the importance of rapid remediation. 8) For environments where immediate patching is not feasible, consider disabling UPnP services on affected devices to reduce the attack surface.