CVE-2026-3400 is a stack-based buffer overflow vulnerability identified in the Tenda AC15 wireless router series, specifically affecting firmware versions from 15.13.07.0 through 15.13.07.13. The vulnerability resides in an unknown functionality related to the /goform/TextEditingConversion endpoint, where the argument wpapsk_crypto2_4g is improperly handled. By crafting a malicious request that manipulates this argument, an attacker can overflow the stack buffer, potentially overwriting critical memory regions. This can lead to arbitrary code execution with elevated privileges on the device. The attack vector is remote network access, requiring no authentication or user interaction, which significantly increases the risk. The CVSS 4.0 base score is 8.7 (high), reflecting the ease of exploitation and the severe impact on confidentiality, integrity, and availability. Although no confirmed exploits in the wild have been reported, a public proof-of-concept exploit exists, increasing the likelihood of exploitation attempts. The vulnerability affects a widely used consumer and small business router model, which is often deployed in home and office environments, making it a critical concern for network security. The lack of available patches at the time of disclosure necessitates immediate mitigation efforts to reduce exposure.

The exploitation of CVE-2026-3400 can have severe consequences for organizations and individuals using Tenda AC15 routers. Successful exploitation allows remote attackers to execute arbitrary code with elevated privileges, potentially leading to full device compromise. This can result in unauthorized access to internal networks, interception or manipulation of network traffic, disruption of network services, and the establishment of persistent backdoors. The confidentiality of sensitive data traversing or stored on the device can be compromised, while integrity and availability of network services may be severely impacted. Given the router's role as a gateway device, attackers could pivot to other internal systems, escalating the scope of the breach. The ease of remote exploitation without authentication or user interaction increases the threat level, especially in environments where these routers are exposed directly to the internet or poorly segmented networks. This vulnerability poses a significant risk to home users, small businesses, and potentially larger organizations relying on Tenda AC15 devices for network connectivity.

1. Immediate mitigation should focus on network-level protections such as restricting access to the router's management interface from untrusted networks, especially the internet. 2. Implement firewall rules to block incoming traffic to the /goform/TextEditingConversion endpoint or the specific parameter wpapsk_crypto2_4g if possible. 3. Monitor network traffic for anomalous requests targeting the vulnerable endpoint to detect potential exploitation attempts. 4. Segment networks to isolate vulnerable devices from critical infrastructure and sensitive data. 5. Regularly check for firmware updates from Tenda and apply patches promptly once released to remediate the vulnerability. 6. Consider replacing affected devices with models from vendors with stronger security track records if patching is delayed or unavailable. 7. Employ intrusion detection/prevention systems (IDS/IPS) with signatures for this vulnerability once available. 8. Educate users and administrators about the risks and signs of exploitation to improve incident response readiness.