CVE-2025-8159 is a critical stack-based buffer overflow vulnerability identified in the D-Link DIR-513 router, specifically version 1.0. The flaw resides in the HTTP POST request handler component, within the function formLanguageChange, which processes requests to the /goform/formLanguageChange endpoint. The vulnerability arises from improper handling of the 'curTime' argument, allowing an attacker to manipulate this input to overflow the stack buffer. This overflow can lead to arbitrary code execution or cause the device to crash, impacting the router's availability and potentially allowing remote attackers to gain control without requiring authentication or user interaction. The vulnerability is remotely exploitable over the network, increasing the risk profile. Although the affected product is no longer supported by D-Link, the exploit code has been publicly disclosed, raising the likelihood of exploitation by threat actors. The CVSS v4.0 score of 8.7 (high severity) reflects the vulnerability's ease of exploitation (no authentication or user interaction needed), and its significant impact on confidentiality, integrity, and availability. No official patches are available due to the product's end-of-life status, complicating remediation efforts. This vulnerability primarily affects legacy deployments of the DIR-513 router, which may still be in use in some environments despite its unsupported status.

For European organizations, the impact of CVE-2025-8159 can be substantial, especially for those relying on legacy network infrastructure that includes the D-Link DIR-513 router. Successful exploitation could lead to full compromise of the affected router, enabling attackers to intercept, manipulate, or disrupt network traffic. This can result in loss of confidentiality of sensitive data, integrity violations through unauthorized configuration changes or traffic redirection, and availability disruptions via device crashes or denial-of-service conditions. Such impacts are critical for enterprises, government agencies, and service providers that depend on secure and reliable network connectivity. Additionally, compromised routers can serve as footholds for lateral movement within internal networks or as launch points for broader attacks, including ransomware or espionage campaigns. The lack of vendor support and patches increases the risk, as organizations must rely on alternative mitigation strategies. Given the public availability of exploit code, the threat landscape is heightened, and opportunistic attackers may target vulnerable devices in European networks, particularly those with insufficient network segmentation or outdated asset inventories.

Since no official patches are available for the DIR-513 due to its end-of-life status, European organizations should prioritize the following specific mitigation steps: 1) Immediate identification and inventory of all DIR-513 devices within the network to assess exposure. 2) Segmentation or isolation of affected devices from critical network segments to limit potential lateral movement and data exposure. 3) Replacement of DIR-513 routers with supported, updated hardware that receives security patches and vendor support. 4) If immediate replacement is not feasible, implement strict firewall rules to block external and internal access to the /goform/formLanguageChange endpoint or restrict HTTP POST requests to trusted management hosts only. 5) Continuous network monitoring and anomaly detection focused on unusual traffic patterns or attempts to exploit the vulnerability. 6) Employ network intrusion detection/prevention systems (IDS/IPS) with signatures or heuristics capable of detecting exploitation attempts targeting this vulnerability. 7) Educate IT and security teams about the risks associated with unsupported legacy devices and the importance of timely hardware lifecycle management. These targeted actions go beyond generic advice by focusing on compensating controls and asset management tailored to this specific vulnerability and product lifecycle context.