CVE-2026-2138 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_42D03C within the /goform/SetStaticRouteCfg endpoint. This function improperly processes the argument list, allowing an attacker to craft a malicious request that overflows a buffer. The overflow can be triggered remotely without requiring authentication or user interaction, making it highly exploitable over the network. The vulnerability can lead to arbitrary code execution, enabling attackers to gain control over the router, disrupt network traffic, or pivot into internal networks. The CVSS 4.0 score of 8.7 reflects the high impact on confidentiality, integrity, and availability, combined with low attack complexity and no required privileges. Although no exploits have been observed in the wild yet, the public release of exploit code increases the likelihood of imminent attacks. The lack of available patches at the time of publication necessitates immediate mitigation through network segmentation and access restrictions. This vulnerability is critical for organizations relying on Tenda TX9 routers, especially those exposing management interfaces to untrusted networks.

For European organizations, exploitation of CVE-2026-2138 could result in full compromise of Tenda TX9 routers, leading to interception or manipulation of network traffic, disruption of services, and potential lateral movement within corporate networks. Confidential data traversing these routers could be exposed or altered, undermining data integrity and privacy obligations under regulations such as GDPR. The availability of network services could be impacted by denial-of-service conditions caused by the exploit. Critical infrastructure sectors, including telecommunications, finance, and government agencies using these routers, face heightened risk of operational disruption and espionage. The remote and unauthenticated nature of the vulnerability increases the attack surface, especially for organizations with inadequate network segmentation or exposed router management interfaces. The public availability of exploit code further elevates the threat level, necessitating urgent defensive measures to prevent exploitation and potential large-scale incidents.

1. Immediately audit network configurations to identify Tenda TX9 routers running vulnerable firmware versions. 2. Restrict access to the /goform/SetStaticRouteCfg endpoint by implementing firewall rules or access control lists limiting management interface exposure to trusted internal networks only. 3. Employ network segmentation to isolate vulnerable devices from critical assets and sensitive data flows. 4. Monitor network traffic for anomalous requests targeting the /goform/SetStaticRouteCfg endpoint or unusual patterns indicative of exploitation attempts. 5. Engage with Tenda support channels to obtain and apply firmware updates or patches as soon as they become available. 6. If patches are unavailable, consider temporary device replacement or disabling remote management features to reduce exposure. 7. Implement intrusion detection/prevention systems (IDS/IPS) with signatures targeting this specific vulnerability or exploit behavior. 8. Educate network administrators about the vulnerability and encourage prompt incident reporting and response readiness. 9. Maintain up-to-date asset inventories to track affected devices and ensure timely remediation. 10. Conduct regular vulnerability assessments and penetration testing focusing on network infrastructure devices to detect similar issues proactively.