CVE-2022-40876 is a critical remote code execution (RCE) vulnerability identified in the Tenda AX1803 router firmware version 1.0.0.1. The vulnerability arises from improper handling of HTTP requests processed by the functions fromAdvSetMacMtuWan, specifically parameters such as wanSpeed, cloneType, and mac. These functions fail to properly validate or sanitize input, leading to a stack-based buffer overflow (CWE-787). Exploiting this flaw allows an unauthenticated attacker to send specially crafted HTTP requests to the device, causing a stack overflow that can overwrite the execution stack and enable arbitrary code execution remotely without any user interaction or privileges. The CVSS 3.1 base score of 9.8 reflects the criticality, with attack vector being network-based (AV:N), no privileges required (PR:N), no user interaction (UI:N), and full impact on confidentiality, integrity, and availability (C:H/I:H/A:H). Although no public exploits are currently known in the wild, the vulnerability’s nature and ease of exploitation make it a significant threat to affected devices. The lack of vendor or product details beyond the Tenda AX1803 router limits broader scope identification, but the vulnerability specifically targets the router’s WAN interface management functions, which are commonly exposed to the internet, increasing the attack surface. This vulnerability could be leveraged by attackers to gain persistent control over the router, intercept or manipulate network traffic, launch further attacks on internal networks, or disrupt internet connectivity.

For European organizations, the impact of CVE-2022-40876 can be substantial, particularly for small and medium enterprises (SMEs) and home office environments relying on Tenda AX1803 routers for internet connectivity. Successful exploitation could lead to full compromise of the router, enabling attackers to intercept sensitive communications, redirect traffic to malicious sites, or establish persistent footholds within corporate or home networks. This can result in data breaches, intellectual property theft, or disruption of business operations. Given the criticality and network exposure, attackers could use compromised routers as launchpads for lateral movement or as part of botnets for distributed denial-of-service (DDoS) attacks, affecting broader network stability. The vulnerability also poses risks to privacy and compliance with European data protection regulations (e.g., GDPR) if personal or sensitive data is intercepted or manipulated. The absence of patches or vendor guidance increases the urgency for organizations to identify and mitigate affected devices proactively.

1. Immediate identification and inventory of Tenda AX1803 routers within the network environment is essential. Network scanning tools can help detect these devices by their signatures or management interfaces. 2. Isolate affected routers from direct internet exposure by placing them behind firewalls or restricting WAN access to trusted IPs only. 3. Disable remote management features on the router if not strictly necessary, especially HTTP-based management interfaces. 4. Monitor network traffic for unusual patterns or unexpected HTTP requests targeting router management endpoints, which may indicate exploitation attempts. 5. Employ network segmentation to limit the impact of a compromised router on critical internal systems. 6. Regularly check for firmware updates or security advisories from Tenda, and apply patches promptly once available. 7. As a longer-term measure, consider replacing vulnerable routers with devices from vendors with strong security track records and active vulnerability management. 8. Implement intrusion detection/prevention systems (IDS/IPS) with signatures or heuristics capable of detecting exploitation attempts targeting this vulnerability. 9. Educate IT staff and users about the risks associated with unmanaged or outdated network devices to foster proactive security practices.