CVE-2025-57059 is a high-severity vulnerability identified in the Tenda G3 router firmware version 3.0br_V15.11.0.17. The issue is a stack-based buffer overflow located in the handling of the dhcpIndex parameter within the addDhcpRule function. This function is responsible for managing DHCP rules on the device. An attacker can exploit this vulnerability by sending a specially crafted request with a malicious dhcpIndex value, causing the router's stack to overflow. This overflow leads to a Denial of Service (DoS) condition, effectively crashing or rebooting the device and disrupting network connectivity. The vulnerability does not require any authentication or user interaction, and it can be exploited remotely over the network (AV:N), making it relatively easy to trigger. The CVSS v3.1 base score is 7.5, indicating a high severity primarily due to the impact on availability (A:H) with no impact on confidentiality or integrity. The vulnerability is categorized under CWE-121, which corresponds to stack-based buffer overflows, a common and dangerous class of memory corruption bugs. No known exploits are currently reported in the wild, and no patches have been published yet. The lack of affected version details beyond the specified firmware version suggests the issue may be limited to this firmware iteration, but users of this version are at risk. Given the nature of the vulnerability, attackers could disrupt business operations by causing network outages, especially in environments relying on these routers for critical connectivity.

For European organizations, the impact of this vulnerability could be significant, particularly for small to medium enterprises and home office setups that use Tenda G3 routers. A successful DoS attack would result in loss of internet connectivity, disrupting business communications, cloud services access, and potentially halting operations dependent on continuous network availability. Critical infrastructure or service providers using these devices as part of their network edge could face operational downtime, leading to financial losses and reputational damage. Additionally, the ease of exploitation without authentication raises the risk of automated attacks or widespread scanning campaigns targeting vulnerable devices. Although the vulnerability does not allow data theft or system compromise beyond DoS, the disruption of network services can have cascading effects on business continuity and incident response capabilities.

Organizations should immediately identify any Tenda G3 routers running firmware version 3.0br_V15.11.0.17 within their networks. Until an official patch is released, mitigation should focus on network-level protections: 1) Restrict access to router management interfaces by implementing firewall rules that limit incoming traffic to trusted IP addresses only. 2) Disable remote management features if not required to reduce exposure. 3) Monitor network traffic for unusual DHCP-related requests that could indicate exploitation attempts. 4) Consider segmenting networks to isolate vulnerable devices from critical systems. 5) Engage with Tenda support channels to obtain information on forthcoming patches or firmware updates addressing this vulnerability. 6) Plan for rapid deployment of firmware updates once available. 7) Employ intrusion detection/prevention systems (IDS/IPS) with signatures targeting DHCP-related anomalies to detect and block exploit attempts. These steps go beyond generic advice by focusing on immediate containment and detection strategies tailored to the specific vulnerability vector.