CVE-2026-26732 is a stack-based buffer overflow vulnerability identified in the TOTOLINK A3002RU router firmware version V2.1.1-B20211108.1455. The vulnerability arises in the formFilter function when processing the vpnUser or vpnPassword parameters, which are likely part of the router's VPN configuration interface. A stack-based buffer overflow occurs when input data exceeds the allocated buffer size on the stack, potentially overwriting adjacent memory and enabling arbitrary code execution or causing a system crash. This vulnerability can be exploited remotely if the router's management or VPN configuration interface is accessible over the network, as no authentication is indicated as required. Exploiting this flaw could allow attackers to execute arbitrary code with the privileges of the router's firmware process, leading to full compromise of the device, interception or manipulation of VPN traffic, or denial of service by crashing the device. No public exploits or patches are currently available, and no CVSS score has been assigned yet. The vulnerability affects the confidentiality, integrity, and availability of the device and any connected networks. Given the nature of the vulnerability and the lack of authentication, the risk is significant, especially for organizations relying on this router for VPN connectivity and secure communications.

For European organizations, this vulnerability poses a serious risk to network security and operational continuity. Exploitation could lead to unauthorized access to internal networks via compromised VPN credentials or manipulation of VPN traffic, undermining confidentiality and data integrity. The ability to execute arbitrary code on the router could allow attackers to establish persistent footholds, intercept sensitive communications, or launch further attacks within the network. Denial of service attacks could disrupt business operations by rendering VPN services unavailable. Organizations in sectors such as finance, healthcare, government, and critical infrastructure that rely heavily on secure VPN connections are particularly vulnerable. The lack of authentication requirement and potential for remote exploitation increase the threat level, especially if devices are exposed to the internet or poorly segmented networks. The absence of patches or mitigations at present means organizations must act proactively to reduce exposure.

1. Immediately restrict access to the router's management and VPN configuration interfaces to trusted internal networks only, using firewall rules and network segmentation. 2. Disable remote management and VPN configuration access from untrusted networks or the internet. 3. Monitor network traffic for unusual activity related to VPN authentication attempts or router management interfaces. 4. Contact TOTOLINK for firmware updates or security advisories addressing this vulnerability and apply patches as soon as they become available. 5. Consider replacing vulnerable devices with models from vendors with a stronger security track record if patches are delayed. 6. Implement network-level intrusion detection/prevention systems (IDS/IPS) to detect exploitation attempts targeting this vulnerability. 7. Educate IT staff on the risks and signs of exploitation related to this vulnerability to enable rapid incident response.