CVE-2025-9783 is a high-severity buffer overflow vulnerability identified in the TOTOLINK A702R router, specifically affecting firmware version 4.0.0-B20211108.1423. The vulnerability resides in the function sub_418030 within the /boafrm/formParentControl file. An attacker can exploit this flaw by manipulating the 'submit-url' argument, which leads to a buffer overflow condition. This vulnerability is remotely exploitable without requiring user interaction or prior authentication, making it particularly dangerous. The CVSS 4.0 base score is 8.7, reflecting the ease of remote exploitation (attack vector: network), low attack complexity, no privileges required, and no user interaction needed. The impact on confidentiality, integrity, and availability is high, indicating that successful exploitation could allow an attacker to execute arbitrary code, potentially leading to full system compromise, data leakage, or denial of service. Although no public exploits are currently known to be actively used in the wild, the vulnerability has been publicly disclosed, increasing the risk of exploitation by threat actors. The TOTOLINK A702R is a consumer and small business-grade wireless router, and the affected firmware version is from late 2021. The vulnerability's presence in a network device that often serves as a gateway to internal networks amplifies the risk, as attackers could leverage this to pivot into internal systems or disrupt network operations.

For European organizations, the exploitation of CVE-2025-9783 could have significant consequences. Many small and medium enterprises (SMEs) and residential users rely on TOTOLINK routers for internet connectivity. A successful attack could lead to unauthorized access to internal networks, interception of sensitive communications, or disruption of internet services. This is particularly critical for organizations with remote or hybrid work models, where secure and reliable home or branch office connectivity is essential. Additionally, compromised routers could be used as footholds for launching further attacks, including lateral movement within corporate networks or participation in botnets. The high severity and remote exploitability mean that attackers can target vulnerable devices at scale, potentially impacting critical infrastructure sectors such as finance, healthcare, and government agencies that may use these devices in less secure environments. The lack of available patches or mitigations at the time of disclosure further exacerbates the risk, necessitating immediate attention from affected organizations.

Given the absence of official patches or firmware updates at the time of disclosure, European organizations should implement several targeted mitigation strategies. First, identify and inventory all TOTOLINK A702R devices running the affected firmware version within their networks. Network segmentation should be employed to isolate vulnerable routers from critical internal systems, limiting potential lateral movement. Disable remote management interfaces on these devices to reduce exposure to external attackers. Implement strict firewall rules to restrict inbound traffic to the router management ports and monitor network traffic for unusual patterns indicative of exploitation attempts. Where possible, replace vulnerable devices with updated hardware or firmware versions that address the vulnerability. Additionally, organizations should deploy intrusion detection/prevention systems (IDS/IPS) with signatures or heuristics capable of detecting exploitation attempts targeting the 'submit-url' parameter. Regularly review vendor communications for firmware updates and apply them promptly once available. Educate users and administrators about the risks associated with this vulnerability and encourage vigilance regarding unusual device behavior or network anomalies.