CVE-2025-71027 is a stack overflow vulnerability identified in the Tenda AX-3 router firmware version v16.03.12.10_CN. The flaw exists in the handling of the wanMTU2 parameter within the fromAdvSetMacMtuWan function. A stack overflow occurs when this parameter is manipulated with a crafted request, leading to memory corruption that can crash the device or disrupt its normal operation. This results in a Denial of Service (DoS) condition, rendering the router unavailable to legitimate users. The vulnerability does not require authentication or user interaction, which means an attacker can exploit it remotely by sending malicious packets to the router’s management interface or WAN side if exposed. No CVSS score has been assigned yet, and no public exploits have been reported, but the nature of the vulnerability suggests it could be leveraged to disrupt network connectivity. The affected device, Tenda AX-3, is a popular consumer and small business router model, often deployed in home and small office environments. The lack of a patch or mitigation details at this time increases the urgency for affected users to restrict access and monitor for updates.

For European organizations, the primary impact of CVE-2025-71027 is on network availability. A successful exploit can cause routers to crash or become unresponsive, leading to loss of internet connectivity and disruption of business operations, especially for small and medium enterprises relying on Tenda AX-3 devices. This could affect remote work, cloud service access, and internal communications. While the vulnerability does not directly compromise confidentiality or integrity, the resulting DoS could be leveraged as part of a larger attack chain or to distract security teams. The impact is more pronounced in environments where these routers are used as primary gateways without redundant failover. Additionally, service providers or managed security service providers (MSSPs) that deploy Tenda AX-3 routers for clients could face broader service disruptions.

1. Immediately restrict external access to the router’s management interfaces, especially from the WAN side, to prevent remote exploitation. 2. Implement network segmentation to isolate vulnerable devices from critical infrastructure. 3. Monitor network traffic for unusual or malformed packets targeting the wanMTU2 parameter or related router functions. 4. Regularly check Tenda’s official channels for firmware updates or security advisories addressing this vulnerability and apply patches promptly once available. 5. Consider replacing Tenda AX-3 routers with alternative devices from vendors with a stronger security track record if patching is delayed. 6. Employ intrusion detection/prevention systems (IDS/IPS) with signatures or heuristics to detect exploitation attempts. 7. Educate IT staff about this vulnerability to ensure rapid response to any signs of exploitation or device instability.