CVE-2025-57063 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 handling of the portMappingIndex parameter within the formDelPortMapping function. This vulnerability arises when the router processes a specially crafted request that manipulates the portMappingIndex parameter, leading to a stack overflow condition. Exploiting this flaw does not require any authentication or user interaction, and the attacker can trigger a Denial of Service (DoS) state by causing the router to crash or become unresponsive. The vulnerability is classified under CWE-121, which corresponds to stack-based buffer overflows, a common and dangerous class of memory corruption issues. The CVSS v3.1 base score is 7.5, indicating a high severity due to the network attack vector (AV:N), low attack complexity (AC:L), no privileges required (PR:N), and no user interaction (UI:N). The impact is limited to availability (A:H), with no confidentiality or integrity impact reported. No known exploits are currently observed in the wild, and no patches have been published yet. This vulnerability affects the specific Tenda G3 router firmware version mentioned, which is commonly used in home and small office environments for network routing and port forwarding management.

For European organizations, the primary impact of this vulnerability is the potential disruption of network services due to router crashes or reboots triggered by malicious crafted requests. This can lead to temporary loss of internet connectivity, interruption of business operations, and potential cascading effects on dependent services such as VoIP, VPNs, and internal communications. While the vulnerability does not directly compromise data confidentiality or integrity, the availability impact can be significant, especially for small and medium enterprises (SMEs) relying on Tenda G3 routers for critical network functions. Additionally, denial of service conditions can be exploited as part of larger multi-vector attacks or to create distractions while other attacks are conducted. The lack of authentication requirement means that any attacker with network access, including remote attackers over the internet if the router's management interface is exposed, can exploit this vulnerability. This raises concerns for organizations with less stringent network perimeter controls or remote management enabled on these devices.

To mitigate this vulnerability, European organizations should first identify any Tenda G3 routers running the affected firmware version 3.0br_V15.11.0.17 within their networks. Immediate steps include restricting access to the router's management interfaces by disabling remote management over the internet and limiting access to trusted internal IP addresses only. Network segmentation should be employed to isolate vulnerable devices from critical infrastructure. Monitoring network traffic for unusual or malformed requests targeting the portMappingIndex parameter can help detect exploitation attempts. Since no official patches are currently available, organizations should contact Tenda support for firmware updates or advisories. As a temporary workaround, disabling port mapping features or services that invoke the vulnerable function may reduce exposure. Additionally, implementing network-level protections such as intrusion prevention systems (IPS) with custom signatures to detect and block exploit attempts is recommended. Regularly updating router firmware once patches are released is essential to fully remediate the vulnerability.