CVE-2025-57070 is a high-severity vulnerability identified in the Tenda G3 router firmware version 3.0br_V15.11.0.17. The flaw is a stack-based buffer overflow occurring in the gstUp parameter within the guestWifiRuleRefresh function. This vulnerability arises when the router processes a specially crafted request that manipulates the gstUp parameter, leading to a stack overflow condition. Such a condition can overwrite critical memory regions, destabilizing the device's operation and causing a Denial of Service (DoS). The vulnerability does not require any authentication or user interaction, and can be exploited remotely over the network (AV:N, PR:N, UI:N). The CVSS v3.1 base score is 7.5, reflecting a high impact on availability (A:H) but no direct impact on confidentiality or integrity. The underlying weakness corresponds to CWE-121, a classic stack-based buffer overflow, which is a well-known and dangerous class of vulnerabilities. No patches or known exploits in the wild have been reported yet. The vulnerability affects the Tenda G3 router, a consumer and small office networking device, which is commonly used to provide Wi-Fi connectivity including guest network functionality. The guestWifiRuleRefresh function likely manages guest Wi-Fi access rules, and the gstUp parameter is presumably part of the input controlling these rules. Exploiting this flaw can cause the router to crash or reboot, disrupting network availability for users relying on the device.

For European organizations, especially small and medium enterprises (SMEs) and home offices that use Tenda G3 routers, this vulnerability poses a significant risk to network availability. A successful exploit can cause network outages by crashing the router, leading to loss of internet connectivity and disruption of business operations. While the vulnerability does not directly compromise data confidentiality or integrity, the resulting DoS can impact productivity and availability of critical services. In environments where guest Wi-Fi access is used to segregate visitor traffic, this vulnerability could be leveraged to disrupt network segmentation policies, potentially increasing exposure to other threats. Additionally, if attackers use this DoS as a distraction, it could facilitate other attacks during the downtime. Given the ease of exploitation (no authentication or user interaction required), attackers can remotely target vulnerable routers, including those exposed to the internet or accessible from local networks. This is particularly concerning for organizations with limited IT security management or outdated network equipment. The lack of patches increases the window of exposure, emphasizing the need for immediate mitigation.

1. Network Segmentation: Isolate Tenda G3 routers from critical network segments and restrict access to management interfaces to trusted IP addresses only. 2. Access Controls: Implement firewall rules to block unsolicited inbound traffic to the router’s management ports from untrusted networks, especially the internet. 3. Disable Guest Wi-Fi: If guest Wi-Fi functionality is not essential, disable it to reduce the attack surface related to the vulnerable guestWifiRuleRefresh function. 4. Monitor Network Traffic: Deploy intrusion detection/prevention systems (IDS/IPS) to detect anomalous requests targeting the gstUp parameter or unusual traffic patterns indicative of exploitation attempts. 5. Vendor Engagement: Regularly check for firmware updates or security advisories from Tenda and apply patches immediately once available. 6. Device Replacement: For critical environments, consider replacing vulnerable Tenda G3 routers with devices from vendors with stronger security track records and timely patch management. 7. Incident Response Preparation: Prepare to quickly respond to DoS incidents by having backup connectivity options and procedures to reset or reconfigure affected routers. 8. User Awareness: Educate network administrators about this vulnerability and the importance of restricting router management access.