CVE-2025-9046 is a high-severity stack-based buffer overflow vulnerability identified in the Tenda AC20 router firmware version 16.03.08.12. The flaw exists in the function sub_46A2AC within the /goform/setMacFilterCfg endpoint, which processes the deviceList argument. Improper handling of this argument allows an attacker to overflow the stack buffer, potentially overwriting critical memory regions. This vulnerability can be exploited remotely without user interaction or prior authentication, as indicated by the CVSS vector (AV:N/AC:L/AT:N/UI:N/PR:L). The exploit manipulates the deviceList parameter to trigger the overflow, which could lead to arbitrary code execution, denial of service, or complete compromise of the device. Although no known exploits have been observed in the wild yet, the public disclosure of the exploit code increases the risk of imminent attacks. The vulnerability impacts the confidentiality, integrity, and availability of the affected device, given the high impact scores (VC:H/VI:H/VA:H). The Tenda AC20 is a consumer-grade wireless router commonly used in home and small office environments, making this vulnerability significant for network security. The lack of an official patch link suggests that mitigation options may currently be limited to workarounds or firmware updates from the vendor once available.

For European organizations, especially small businesses and home offices relying on Tenda AC20 routers, this vulnerability poses a substantial risk. Successful exploitation could allow attackers to gain control over the router, intercept or manipulate network traffic, and pivot into internal networks. This could lead to data breaches, disruption of business operations, and compromise of connected devices. Given the remote and unauthenticated nature of the exploit, attackers could scan for vulnerable devices across Europe and launch automated attacks. The impact is particularly critical for organizations with limited IT security resources or those that have not updated their network equipment firmware regularly. Additionally, compromised routers could be used as part of botnets or for launching further attacks, amplifying the threat landscape in the region.

1. Immediate mitigation should include isolating affected Tenda AC20 devices from critical network segments to limit potential lateral movement. 2. Network administrators should monitor traffic for unusual patterns or attempts to access the /goform/setMacFilterCfg endpoint. 3. Implement network-level filtering to block or restrict access to the router’s management interface from untrusted networks, especially the WAN side. 4. Disable remote management features if enabled to reduce exposure. 5. Regularly check for firmware updates from Tenda and apply patches as soon as they become available. 6. Consider replacing vulnerable devices with models from vendors with a stronger security track record if patches are delayed. 7. Employ network intrusion detection systems (NIDS) to detect exploitation attempts targeting this vulnerability. 8. Educate users about the risks of using outdated router firmware and encourage proactive security hygiene.