CVE-2025-11339 is a remote buffer overflow vulnerability identified in the D-Link DI-7100G C1 device, specifically within the jhttpd web server component. The vulnerability exists in the function sub_4BD4F8 of the /webchat/hi_block.asp file, where improper validation and handling of the popupId argument leads to a buffer overflow condition. This flaw can be exploited by an unauthenticated attacker remotely by sending a specially crafted request to the vulnerable endpoint, causing memory corruption. The buffer overflow can potentially allow arbitrary code execution, leading to full compromise of the device, including unauthorized access, data manipulation, or denial of service. The vulnerability affects firmware versions up to 20250928, and the CVSS 4.0 score is 8.7, indicating high severity with network attack vector, low attack complexity, no privileges or user interaction required, but with high impact on confidentiality, integrity, and availability. Although no active exploits have been observed in the wild, public exploit code has been disclosed, increasing the likelihood of exploitation attempts. The vulnerability is critical for environments relying on these devices for network connectivity or communication services, as compromise could lead to lateral movement within networks or disruption of services.

For European organizations, the impact of CVE-2025-11339 can be severe. The D-Link DI-7100G C1 is often deployed in enterprise and telecom environments, and exploitation could lead to unauthorized remote control of network devices. This compromises confidentiality by exposing sensitive network traffic or credentials, integrity by allowing attackers to alter device configurations or data, and availability by causing device crashes or network outages. Critical infrastructure sectors such as telecommunications, government agencies, and large enterprises are at heightened risk due to their reliance on stable and secure network devices. The public disclosure of exploit code increases the risk of opportunistic attacks, potentially leading to widespread disruption. Additionally, compromised devices could be leveraged as pivot points for further attacks within organizational networks, amplifying the overall security risk.

1. Immediate action should be taken to check for firmware updates from D-Link addressing this vulnerability; apply patches as soon as they become available. 2. If patches are not yet released, restrict network access to the vulnerable device’s management interfaces, especially blocking access to the /webchat/hi_block.asp endpoint from untrusted networks. 3. Employ network segmentation to isolate vulnerable devices from critical network segments. 4. Implement intrusion detection/prevention systems (IDS/IPS) with signatures or heuristics to detect attempts to exploit buffer overflow conditions targeting the popupId parameter. 5. Regularly audit and monitor device logs for unusual activity or repeated access attempts to the vulnerable endpoint. 6. Consider deploying web application firewalls (WAF) or reverse proxies to filter malicious payloads targeting the affected function. 7. Educate network administrators on the risks and signs of exploitation to enable rapid incident response. 8. Maintain an inventory of all D-Link DI-7100G C1 devices in use to ensure comprehensive coverage of mitigation efforts.