CVE-2025-10666 is a high-severity buffer overflow vulnerability affecting the D-Link DIR-825 router models running firmware versions up to 2.10. The flaw exists in the apply.cgi component, specifically in the function sub_4106d4, where improper handling of the countdown_time argument allows an attacker to overflow a buffer. This vulnerability can be exploited remotely without user interaction or authentication, as indicated by the CVSS vector (AV:N/AC:L/AT:N/UI:N/PR:L). The buffer overflow can lead to arbitrary code execution with high impact on confidentiality, integrity, and availability of the device. Although the affected products are no longer supported by the vendor, the exploit code has been publicly released, increasing the risk of exploitation. The vulnerability does not require user interaction and can be triggered over the network, making it a critical risk for exposed devices. The lack of vendor patches means that affected devices remain vulnerable unless mitigated by other means. The vulnerability’s CVSS 4.0 score is 8.7, reflecting its high severity and ease of exploitation. The router’s role as a network gateway means compromise could lead to network-wide impacts, including interception or manipulation of traffic, lateral movement, or use as a foothold for further attacks.

For European organizations, this vulnerability poses a significant risk, especially for those still operating legacy D-Link DIR-825 routers. Compromise could lead to unauthorized access to internal networks, data interception, and disruption of network services. Given the router’s position at the network perimeter, attackers could leverage this flaw to bypass security controls, pivot to internal systems, or launch further attacks such as ransomware or espionage. The lack of vendor support means no official patches are available, increasing the likelihood of exploitation in the wild once exploit code is widely used. Organizations relying on these devices for critical connectivity or in sensitive environments face risks to confidentiality, integrity, and availability of their communications and data. The vulnerability’s remote, unauthenticated exploitability exacerbates the threat, particularly for organizations with routers exposed to the internet or poorly segmented networks.

Since no official patches are available due to end-of-life status, European organizations should prioritize immediate mitigation steps: 1) Replace affected D-Link DIR-825 routers with currently supported and patched models from reputable vendors to eliminate the vulnerability. 2) If replacement is not immediately feasible, isolate affected devices from direct internet exposure by placing them behind additional firewalls or VPN gateways to restrict access to trusted management networks only. 3) Employ network segmentation to limit the impact of a compromised router and monitor traffic for unusual patterns indicative of exploitation attempts. 4) Implement strict access control lists (ACLs) to block unsolicited inbound traffic targeting the router’s management interfaces. 5) Conduct regular network scans and vulnerability assessments to identify any remaining vulnerable devices. 6) Educate IT staff about the risks of using unsupported hardware and the importance of timely hardware lifecycle management. 7) Consider deploying intrusion detection/prevention systems (IDS/IPS) with signatures for known exploits targeting this vulnerability to detect and block attack attempts.