CVE-2026-2140 is a buffer overflow vulnerability identified in the Tenda TX9 router firmware versions up to 22.03.02.10_multi. The vulnerability resides in the function sub_4223E0 within the /goform/setMacFilterCfg endpoint, which processes the deviceList argument. Improper handling of this argument allows an attacker to overflow a buffer, leading to memory corruption. This flaw can be exploited remotely over the network without requiring user interaction or elevated privileges, making it highly accessible to attackers. The buffer overflow can enable arbitrary code execution or cause denial of service conditions, compromising the confidentiality, integrity, and availability of the affected device. The vulnerability has a CVSS 4.0 base score of 8.7, indicating high severity, with attack vector network (AV:N), low attack complexity (AC:L), no privileges required (PR:L), no user interaction (UI:N), and high impact on confidentiality, integrity, and availability (C:H, I:H, A:H). Although no active exploits have been reported in the wild, a public exploit is available, increasing the risk of exploitation. The Tenda TX9 is a widely used consumer and small business router, and compromised devices could be leveraged for lateral movement, network reconnaissance, or as entry points into corporate networks. The lack of available patches at the time of disclosure necessitates immediate mitigation steps to reduce exposure.

For European organizations, this vulnerability poses significant risks. Exploitation can lead to full compromise of affected routers, enabling attackers to intercept, modify, or disrupt network traffic, potentially affecting sensitive data confidentiality and network availability. Organizations relying on Tenda TX9 routers for perimeter security or internal segmentation may face increased risk of lateral movement by attackers. Critical infrastructure operators and enterprises with remote management enabled are particularly vulnerable. The widespread use of Tenda devices in Europe, especially in small and medium enterprises and residential environments, increases the attack surface. A successful exploit could facilitate espionage, data theft, or disruption of services, impacting business continuity and regulatory compliance under GDPR. The remote, unauthenticated nature of the attack vector further amplifies the threat, making it easier for attackers to target vulnerable devices across the region.

1. Immediately restrict access to the router’s management interface by disabling remote administration or limiting it to trusted IP addresses via firewall rules. 2. Monitor network traffic for unusual activity targeting the /goform/setMacFilterCfg endpoint or unexpected deviceList parameter usage. 3. Deploy network intrusion detection/prevention systems (IDS/IPS) with signatures tuned to detect exploitation attempts of this buffer overflow. 4. Isolate Tenda TX9 devices on segmented network zones to limit potential lateral movement if compromised. 5. Regularly audit and inventory network devices to identify all Tenda TX9 routers and verify firmware versions. 6. Apply vendor-provided patches or firmware updates as soon as they become available. 7. Educate IT staff about this vulnerability and ensure incident response plans include scenarios involving router compromise. 8. Consider temporary replacement or additional protective controls for critical environments until patches are deployed.