CVE-2025-8131 is a critical stack-based buffer overflow vulnerability identified in the Tenda AC20 router firmware version 16.03.08.05. The vulnerability resides in an unspecified functionality within the /goform/SetStaticRouteCfg endpoint. This endpoint likely handles configuration of static routing parameters on the device. The vulnerability arises from improper handling of the argument list passed to this endpoint, allowing an attacker to craft a malicious request that overflows a stack buffer. This overflow can corrupt adjacent memory, potentially enabling arbitrary code execution or causing denial of service conditions. The vulnerability is remotely exploitable without requiring user interaction or prior authentication, as indicated by the CVSS vector (AV:N/AC:L/AT:N/UI:N/PR:L). The CVSS 4.0 base score is 8.7, categorizing it as a high-severity issue. The exploit has been publicly disclosed, increasing the risk of active exploitation, although no confirmed exploits in the wild have been reported yet. The vulnerability affects only the specific firmware version 16.03.08.05 of the Tenda AC20 router, a consumer-grade wireless access point device. The lack of available patches or vendor advisories at the time of publication suggests that affected users remain vulnerable. Given the nature of the vulnerability, successful exploitation could allow attackers to gain control over the router, manipulate network traffic, intercept sensitive data, or pivot into internal networks. The absence of authentication requirements and the remote attack vector make this a significant threat to network security.

For European organizations, this vulnerability poses a substantial risk, especially for small and medium enterprises (SMEs) and home office environments that commonly deploy consumer-grade routers like the Tenda AC20. Compromise of these routers can lead to interception and manipulation of internal network traffic, undermining confidentiality and integrity of communications. Attackers gaining control over the router could deploy persistent backdoors, redirect DNS queries to malicious servers, or launch further attacks against internal assets. This is particularly concerning for organizations with remote or hybrid workforces relying on such devices for secure connectivity. Additionally, critical infrastructure sectors that utilize these routers for non-enterprise networking purposes could face operational disruptions or data breaches. The lack of patches and public exploit availability increases the urgency for mitigation. The vulnerability could also be leveraged in botnet campaigns or large-scale attacks targeting European networks, amplifying its impact.

1. Immediate mitigation should include isolating affected Tenda AC20 devices from critical network segments and restricting remote management access, especially from untrusted networks. 2. Network administrators should monitor network traffic for unusual activity indicative of exploitation attempts targeting the /goform/SetStaticRouteCfg endpoint. 3. Deploy network-level protections such as Web Application Firewalls (WAFs) or Intrusion Prevention Systems (IPS) with signatures tuned to detect exploitation attempts against this vulnerability. 4. Where possible, replace affected Tenda AC20 routers with devices from vendors providing timely security updates and support. 5. If replacement is not immediately feasible, consider disabling remote management features or restricting access to trusted IP addresses only. 6. Regularly check for vendor firmware updates or security advisories addressing this vulnerability and apply patches promptly once available. 7. Educate users and IT staff about the risks associated with consumer-grade network equipment and encourage adoption of security best practices including network segmentation and strong device configuration.