CVE-2022-40862 is a critical stack overflow vulnerability identified in Tenda AC15 and AC18 routers running firmware version V15.03.05.19. The vulnerability exists in the function fromNatStaticSetting, which processes requests sent to the /goform/NatStaticSetting endpoint. A stack overflow occurs when the function improperly handles input data, allowing an attacker to overwrite parts of the stack memory. This can lead to arbitrary code execution, potentially enabling an attacker to take full control of the affected router without requiring any authentication or user interaction. The vulnerability has a CVSS 3.1 base score of 9.8, indicating a critical severity with network attack vector, low attack complexity, no privileges required, and no user interaction needed. The impact includes full compromise of confidentiality, integrity, and availability of the device. Although no public exploits are currently known in the wild, the ease of exploitation and critical impact make this a significant threat. The vulnerability is categorized under CWE-787 (Out-of-bounds Write), a common and dangerous class of memory corruption bugs. The lack of a patch link suggests that no official fix has been publicly released at the time of this report, increasing the urgency for mitigation.

For European organizations, the exploitation of this vulnerability could have severe consequences. Tenda routers are often used in small to medium enterprises and home office environments, which may serve as entry points into larger corporate networks. Successful exploitation could allow attackers to gain persistent access to internal networks, intercept or manipulate sensitive data, disrupt network availability, or launch further attacks such as lateral movement or ransomware deployment. Given the critical nature of the vulnerability and the absence of authentication requirements, attackers could remotely compromise vulnerable routers en masse. This could lead to widespread network outages, data breaches, and compromise of connected devices. The impact is particularly concerning for sectors reliant on secure and stable network infrastructure, such as finance, healthcare, and critical infrastructure within Europe.

Organizations should immediately identify any Tenda AC15 or AC18 routers running firmware version V15.03.05.19 within their networks. Since no official patch is currently available, the following specific mitigations are recommended: 1) Restrict access to the router management interface by implementing network segmentation and firewall rules to block external access to the /goform/NatStaticSetting endpoint. 2) Disable remote management features on the affected routers to prevent exploitation from outside the local network. 3) Monitor network traffic for unusual requests targeting the vulnerable endpoint and implement intrusion detection/prevention systems with custom signatures to detect exploitation attempts. 4) Where possible, replace vulnerable devices with routers from vendors with active security support and patch management. 5) Regularly check for firmware updates from Tenda and apply patches immediately once available. 6) Educate IT staff and users about the risks associated with outdated router firmware and the importance of network device hygiene.