CVE-2025-34048 is a path traversal vulnerability identified in the web management interface of certain D-Link ADSL routers, specifically the DSL-2730U, DSL-2750U, and DSL-2750E models running firmware versions IN_1.02, SEA_1.04, and SEA_1.07. The vulnerability stems from improper input validation of the 'getpage' parameter within the /cgi-bin/webproc CGI script. An attacker can craft malicious HTTP requests that manipulate this parameter to traverse directories outside the intended restricted directory, thereby accessing arbitrary files on the router's filesystem. This flaw requires no authentication or user interaction, making it remotely exploitable over the network. The impact includes unauthorized disclosure of sensitive files such as configuration files, credentials, or other system data, potentially enabling further attacks or device compromise. The CVSS 4.0 score is 8.7 (high), reflecting the ease of exploitation (network vector, no privileges, no user interaction) and the high confidentiality impact. Although no official patches have been released yet, Shadowserver Foundation observed exploitation attempts in February 2025, indicating active threat actors targeting this vulnerability. The affected devices are commonly used in home and small business environments, but may also be present in enterprise or critical infrastructure networks, increasing the potential impact. The vulnerability is categorized under CWE-22 (Improper Limitation of a Pathname to a Restricted Directory) and CWE-20 (Improper Input Validation).

For European organizations, this vulnerability can lead to significant confidentiality breaches by exposing sensitive router files, including configuration data and credentials, which can facilitate further network compromise. In environments where these routers serve as gateways or are part of critical infrastructure, attackers could leverage this access to pivot into internal networks, disrupt services, or exfiltrate data. The lack of authentication requirement and ease of exploitation increase the risk of widespread attacks, especially in organizations with remote or unmanaged network devices. Small and medium enterprises using these D-Link models without robust network segmentation or monitoring are particularly vulnerable. Additionally, exposure of configuration files could allow attackers to alter device settings or implant persistent backdoors, impacting integrity and availability. The threat is exacerbated by the absence of official patches, requiring organizations to rely on compensating controls. Given the evidence of exploitation in the wild, European entities should consider this vulnerability a serious risk to their network security posture.

1. Immediately restrict access to the router's web management interface by implementing network-level controls such as firewall rules or access control lists to block untrusted or external IP addresses. 2. Disable remote management features on affected devices if not strictly necessary. 3. Monitor network traffic for suspicious requests targeting /cgi-bin/webproc or unusual GET parameters indicative of path traversal attempts. 4. Where possible, upgrade firmware to versions that address this vulnerability once released by D-Link; in the absence of patches, consider device replacement for critical environments. 5. Implement network segmentation to isolate vulnerable routers from sensitive internal networks. 6. Employ intrusion detection/prevention systems (IDS/IPS) with signatures or heuristics to detect exploitation attempts. 7. Conduct regular audits of router configurations and logs to identify unauthorized access or changes. 8. Educate IT staff and users about the risks associated with outdated router firmware and the importance of timely updates. 9. Collaborate with vendors and security communities to stay informed about patch availability and emerging threats related to these devices.