CVE-2025-6334 is a critical stack-based buffer overflow vulnerability identified in the D-Link DIR-867 router, specifically version 1.0. The flaw resides in the Query String Handler component, where improper use of the strncpy function allows an attacker to overflow the stack buffer. This vulnerability can be exploited remotely without requiring user interaction or prior authentication, making it highly accessible to attackers. The overflow can lead to arbitrary code execution, potentially allowing an attacker to take full control of the affected device. The vulnerability affects only the initial version 1.0 of the DIR-867, a product that is no longer supported by D-Link, meaning no official patches or updates are available. Although no known exploits are currently observed in the wild, the public disclosure of the vulnerability increases the risk of exploitation. The CVSS 4.0 score of 8.7 (high severity) reflects the ease of remote exploitation and the significant impact on confidentiality, integrity, and availability, with high impact on all three security objectives. The absence of required privileges and user interaction further elevates the threat level. The vulnerability’s exploitation could allow attackers to execute arbitrary code, disrupt network operations, intercept or manipulate traffic, or use compromised devices as a foothold for further attacks within a network environment.

For European organizations, the exploitation of CVE-2025-6334 poses a substantial risk, especially for those relying on the D-Link DIR-867 1.0 routers in their network infrastructure. Successful exploitation could lead to complete compromise of the affected routers, resulting in network outages, interception of sensitive data, and potential lateral movement within corporate networks. This is particularly critical for sectors with high reliance on network availability and confidentiality, such as finance, healthcare, and critical infrastructure. The lack of vendor support and patches exacerbates the risk, as organizations must rely on mitigations rather than fixes. Additionally, compromised routers could be leveraged as part of botnets or for launching further attacks, increasing the threat landscape. Given the remote exploitability and no need for authentication, attackers can target these devices en masse, potentially impacting large numbers of organizations. The impact extends beyond individual organizations to national cybersecurity posture, especially where these devices are deployed in government or essential service networks.

Since no official patches are available due to the product being out of support, European organizations should implement the following specific mitigations: 1) Immediate inventory and identification of all D-Link DIR-867 version 1.0 devices within the network. 2) Where possible, replace affected devices with currently supported and patched router models to eliminate the vulnerability. 3) If replacement is not immediately feasible, isolate vulnerable routers from direct internet exposure by placing them behind additional firewall layers or VPNs to restrict access to the Query String Handler interface. 4) Employ network segmentation to limit the potential lateral movement from compromised routers to critical internal systems. 5) Monitor network traffic for unusual patterns indicative of exploitation attempts, such as unexpected remote connections or anomalous payloads targeting router management interfaces. 6) Disable or restrict remote management features on affected devices to reduce attack surface. 7) Implement strict access control lists (ACLs) to limit which IP addresses can communicate with the vulnerable router interfaces. 8) Regularly update intrusion detection and prevention systems (IDS/IPS) with signatures related to this vulnerability to detect and block exploitation attempts. 9) Educate IT staff about the risks associated with unsupported hardware and the importance of timely hardware lifecycle management.