CVE-2025-55503 is a stack overflow vulnerability identified in the Tenda AC6 router firmware version V15.03.06.23_multi. The vulnerability arises from improper handling of the 'deviceName' parameter within the saveParentControlInfo function. Specifically, the function fails to adequately validate or limit the size of input data passed to the deviceName parameter, which can lead to a stack overflow condition. Stack overflow vulnerabilities typically allow an attacker to overwrite adjacent memory on the stack, potentially enabling arbitrary code execution, denial of service, or system crashes. Given that this vulnerability exists in a consumer-grade router, exploitation could allow an attacker to gain control over the device or disrupt network operations. The vulnerability does not currently have an assigned CVSS score, nor are there known exploits in the wild at the time of publication. However, the presence of a stack overflow in a network-facing device firmware is a significant security concern. The lack of available patches or mitigations at this time increases the risk for affected users. The vulnerability was published on August 20, 2025, with the reservation date on August 13, 2025, indicating recent discovery. No additional technical details such as exploitation complexity or authentication requirements are provided, but typical stack overflow vulnerabilities in router firmware can often be triggered remotely if the vulnerable function is exposed via the device's management interfaces or network services. This vulnerability specifically targets Tenda AC6 routers, which are widely used in home and small office environments globally.

For European organizations, the impact of this vulnerability could be substantial, particularly for small businesses and home offices relying on Tenda AC6 routers for network connectivity. Successful exploitation could lead to unauthorized remote code execution, allowing attackers to take control of the router, intercept or manipulate network traffic, or launch further attacks within the internal network. This could compromise confidentiality by exposing sensitive data, integrity by altering network configurations or data flows, and availability by causing device crashes or network outages. Given the router's role as a network gateway, exploitation could also facilitate lateral movement to other connected systems, increasing the overall risk posture. The absence of known exploits currently reduces immediate risk, but the potential for future weaponization remains. European organizations with limited IT security resources may be particularly vulnerable due to delayed patching or lack of awareness. Additionally, the vulnerability could be leveraged in botnet recruitment or distributed denial-of-service (DDoS) attacks, indirectly impacting broader network infrastructure in Europe.

To mitigate this vulnerability, European organizations and users of Tenda AC6 routers should first monitor official Tenda communications for firmware updates addressing CVE-2025-55503 and apply patches promptly once available. In the absence of patches, users should restrict access to router management interfaces by disabling remote management features and limiting administrative access to trusted internal networks only. Network segmentation should be employed to isolate vulnerable devices from critical systems. Employing network-level protections such as firewalls to block unsolicited inbound traffic to the router's management ports can reduce exposure. Regularly auditing router configurations and monitoring network traffic for unusual activity can help detect potential exploitation attempts. Organizations should also consider replacing vulnerable devices with models from vendors with stronger security track records if timely patches are not forthcoming. Finally, educating users about the risks of outdated firmware and encouraging routine updates is essential to reduce the attack surface.