CVE-2025-15255 is a critical security vulnerability identified in the Tenda W6-S router firmware version 1.0.0.4(510). The vulnerability is a stack-based buffer overflow located in an unspecified function within the /bin/httpd binary, specifically in the R7websSsecurityHandler component. The flaw is triggered by manipulating the HTTP Cookie header, which is processed by the vulnerable function. Because the HTTP daemon handles incoming web requests, an attacker can remotely send a specially crafted HTTP request with a malicious Cookie value to overflow the stack buffer. This overflow can corrupt the stack, potentially allowing arbitrary code execution or denial of service. The vulnerability requires no authentication or user interaction, making it highly exploitable over the network. The CVSS v4.0 score of 9.3 reflects the critical nature, with network attack vector, low attack complexity, no privileges required, and no user interaction needed. The impact covers confidentiality, integrity, and availability, as successful exploitation could lead to full device compromise, data leakage, or disruption of network services. Although no known exploits are currently observed in the wild, the public disclosure of exploit details increases the likelihood of imminent attacks. The affected product, Tenda W6-S, is a consumer-grade wireless router commonly deployed in home and small office environments. The lack of available patches at the time of disclosure further elevates the risk. This vulnerability underscores the importance of secure coding practices in embedded device firmware, especially in network-facing components like HTTP servers.

The impact of CVE-2025-15255 is severe for organizations and individuals using the Tenda W6-S router. Successful exploitation can lead to arbitrary code execution on the device, allowing attackers to take full control of the router. This can result in interception or manipulation of network traffic, installation of persistent malware, creation of botnets, or complete denial of service. Compromise of the router undermines network perimeter security, potentially exposing internal systems to further attacks. For enterprises relying on these devices in branch offices or remote sites, the vulnerability could serve as an entry point for lateral movement within the corporate network. The lack of authentication and user interaction requirements means attackers can exploit the vulnerability remotely and at scale. The public disclosure of exploit code increases the risk of widespread attacks, especially targeting unpatched devices. The overall impact includes loss of confidentiality, integrity, and availability of network communications and connected systems, posing significant operational and reputational risks.

To mitigate CVE-2025-15255, organizations should first check for and apply any official firmware updates or patches released by Tenda addressing this vulnerability. If no patch is available, immediate steps include disabling remote management interfaces on the Tenda W6-S device to reduce exposure. Network segmentation should be implemented to isolate vulnerable routers from critical infrastructure and sensitive data. Deploying web application firewalls or intrusion prevention systems capable of detecting and blocking malformed HTTP requests with suspicious Cookie headers can help prevent exploitation attempts. Monitoring network traffic for unusual HTTP requests targeting the router’s management interface is recommended. Additionally, consider replacing affected devices with models from vendors with a stronger security track record if patching is not feasible. Educating users about the risks of exposing router management interfaces to the internet and enforcing strong network access controls will further reduce attack surface. Regular vulnerability scanning and penetration testing should include checks for this vulnerability to ensure ongoing protection.