CVE-2026-2191 identifies a critical stack-based buffer overflow vulnerability in the Tenda AC9 router firmware version 15.03.06.42_multi. The vulnerability arises from improper handling of the security.ddos.map argument within the formGetDdosDefenceList function. When this argument is manipulated, it causes a stack overflow, which can be exploited remotely without requiring authentication or user interaction. The overflow can lead to arbitrary code execution with high privileges, potentially allowing attackers to take full control of the device. The CVSS 4.0 score of 8.6 reflects the high impact on confidentiality, integrity, and availability, combined with low attack complexity and no need for privileges or user interaction. Although no active exploits have been reported in the wild, a public exploit is available, increasing the likelihood of exploitation. The vulnerability affects a widely deployed consumer and small business router model, which may be used in home offices, small enterprises, and branch networks. The lack of an official patch or update link in the provided data suggests that remediation options may be limited or delayed, emphasizing the need for alternative mitigations. Attackers exploiting this vulnerability could disrupt network operations, intercept or manipulate traffic, or use the compromised device as a foothold for further attacks within the network.

For European organizations, exploitation of CVE-2026-2191 could lead to significant security breaches, including unauthorized access to internal networks, interception of sensitive communications, and disruption of network availability. Small and medium enterprises (SMEs) and home office setups using Tenda AC9 routers are particularly vulnerable, as these devices often lack robust security monitoring. Compromise of these routers could facilitate lateral movement within corporate networks or serve as entry points for ransomware or espionage campaigns. Critical infrastructure sectors relying on these devices for network connectivity may face operational disruptions. The public availability of an exploit increases the risk of widespread attacks, potentially affecting the confidentiality of personal and corporate data, integrity of network traffic, and availability of internet services. Given the router’s role as a network gateway, successful exploitation could undermine trust in network security and lead to regulatory compliance issues under GDPR and other European data protection laws.

European organizations should immediately assess their network environments for the presence of Tenda AC9 routers running the vulnerable firmware version 15.03.06.42_multi. In the absence of an official patch, organizations should implement network segmentation to isolate vulnerable devices from critical assets. Disable remote management interfaces and restrict access to router administration to trusted internal networks only. Employ intrusion detection and prevention systems (IDS/IPS) to monitor for anomalous traffic patterns targeting the formGetDdosDefenceList function or related endpoints. Regularly update router firmware when vendor patches become available and subscribe to vendor security advisories. Consider replacing vulnerable devices with models from vendors with stronger security track records if patching is not feasible. Additionally, enforce strong network access controls and conduct regular security audits to detect potential compromises early. Educate users about the risks of using outdated router firmware and encourage prompt updates.