CVE-2025-11676 is an improper input validation vulnerability (CWE-20) found in the Universal Plug and Play (UPnP) modules of the TP-Link TL-WR940N V6 router. This vulnerability arises because the device fails to properly validate input data received via UPnP requests, allowing an unauthenticated attacker located on an adjacent network (e.g., same local network or Wi-Fi) to send specially crafted packets that trigger a denial-of-service (DoS) condition. The affected firmware versions include all builds up to 220801. The vulnerability does not require any authentication, user interaction, or privileges, making it relatively easy to exploit by attackers with network proximity. Exploitation results in high impact on availability by causing the device to crash, reboot, or become unresponsive, thereby disrupting network connectivity for users relying on the router. The CVSS 4.0 vector (AV:A/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N) indicates that the attack vector is adjacent network, with low attack complexity, no privileges or user interaction needed, and a high impact on availability. No known exploits have been reported in the wild yet, but the vulnerability is publicly disclosed and assigned a high severity rating. The lack of available patches at the time of disclosure increases the urgency for mitigations. The vulnerability is particularly concerning for environments where these routers are deployed in critical network segments or where network availability is essential. The UPnP service, often enabled by default, expands the attack surface by exposing the vulnerable code to local network attackers. This vulnerability underscores the importance of secure input validation in embedded network devices and the risks posed by UPnP services if not properly secured.

For European organizations, exploitation of CVE-2025-11676 can lead to significant network disruptions due to denial-of-service conditions on widely used TP-Link TL-WR940N V6 routers. This can affect business operations, especially for small and medium enterprises or branch offices relying on these routers for internet connectivity and internal networking. Critical infrastructure sectors such as healthcare, manufacturing, and finance could experience outages impacting service delivery and operational continuity. The unauthenticated nature of the attack means that insider threats or attackers gaining adjacent network access (e.g., via compromised Wi-Fi or guest networks) can easily exploit this vulnerability. Additionally, the disruption of network availability can have cascading effects on connected systems and services, potentially delaying incident response and recovery efforts. Given the prevalence of TP-Link devices in European consumer and enterprise markets, the scope of impact could be broad, affecting both private and public sector networks. The lack of known exploits in the wild currently limits immediate widespread impact, but the public disclosure increases the risk of future exploitation attempts. Organizations with poor network segmentation or weak wireless security controls are particularly vulnerable. The vulnerability does not compromise confidentiality or integrity directly but poses a critical threat to availability, which is a core component of operational security.

1. Monitor TP-Link’s official channels closely for firmware updates addressing CVE-2025-11676 and apply patches promptly once available. 2. Temporarily disable UPnP services on the TL-WR940N V6 routers if business operations allow, as this reduces the attack surface by preventing malicious UPnP requests. 3. Implement strict network segmentation to isolate critical systems from networks where vulnerable routers are deployed, limiting the potential for adjacent attackers to reach the device. 4. Enforce strong Wi-Fi security measures, including WPA3 where possible, to prevent unauthorized adjacent network access. 5. Deploy network intrusion detection/prevention systems (IDS/IPS) with signatures or anomaly detection tuned to identify suspicious UPnP traffic patterns. 6. Conduct regular network audits to identify all TL-WR940N V6 devices and verify firmware versions to prioritize remediation efforts. 7. Educate network administrators and users about the risks of UPnP and the importance of restricting physical and wireless access to trusted parties. 8. Consider replacing vulnerable routers with models that have a stronger security posture and receive timely vendor support if patching is delayed. 9. Maintain robust incident response plans to quickly address potential DoS incidents affecting network availability. These measures collectively reduce the risk of exploitation and mitigate potential operational impacts.