CVE-2026-3400 is a stack-based buffer overflow vulnerability identified in the Tenda AC15 wireless router series, specifically in firmware versions up to 15.13.07.13. The vulnerability resides in an unknown functionality related to the /goform/TextEditingConversion endpoint, where the wpapsk_crypto2_4g parameter is improperly handled. By sending a specially crafted request manipulating this parameter, an attacker can overflow the stack buffer, potentially overwriting control data such as return addresses. This can lead to arbitrary code execution with elevated privileges on the device. The vulnerability is remotely exploitable over the network without requiring authentication or user interaction, making it highly dangerous. The CVSS v4.0 score of 8.7 reflects the ease of exploitation (network attack vector, low complexity, no privileges or user interaction required) and the high impact on confidentiality, integrity, and availability. While no known exploits are currently observed in the wild, public proof-of-concept exploit code has been released, increasing the likelihood of attacks. The vulnerability could allow attackers to take full control of affected routers, leading to network compromise, interception or manipulation of traffic, and use of the device as a pivot point for further attacks.

The impact of CVE-2026-3400 is significant for organizations using Tenda AC15 routers. Successful exploitation can lead to full compromise of the router, allowing attackers to execute arbitrary code with elevated privileges. This can result in interception and manipulation of network traffic, disruption of network availability, and unauthorized access to internal networks. Compromised routers can be used as launch points for lateral movement, data exfiltration, or as part of botnets for distributed denial-of-service (DDoS) attacks. The vulnerability affects confidentiality, integrity, and availability of network communications and infrastructure. Given the remote, unauthenticated exploitability and public availability of exploit code, the risk of widespread attacks is elevated. Organizations relying on these devices for critical network functions or with sensitive data flowing through them face increased exposure to espionage, sabotage, or service disruption.

To mitigate CVE-2026-3400, organizations should immediately inventory their network to identify any Tenda AC15 routers running affected firmware versions. Since no official patches or firmware updates are currently linked, organizations should monitor Tenda's official channels for security updates and apply them promptly once available. In the interim, restrict remote access to router management interfaces by implementing network segmentation and firewall rules that limit access to trusted IP addresses only. Disable remote management features if not required. Employ network intrusion detection/prevention systems (IDS/IPS) with signatures or anomaly detection capable of identifying exploitation attempts targeting /goform/TextEditingConversion or suspicious wpapsk_crypto2_4g parameter activity. Regularly audit router configurations and logs for signs of compromise. Consider replacing affected devices with models from vendors with strong security track records if patches are delayed. Educate network administrators on the risks and signs of exploitation to enable rapid response.