CVE-2025-15255 is a stack-based buffer overflow vulnerability identified in the Tenda W6-S router firmware version 1.0.0.4(510). The vulnerability exists in the /bin/httpd binary, specifically within the R7websSsecurityHandler component that processes HTTP requests. The flaw is triggered by manipulating the Cookie HTTP header argument, which is not properly validated or bounded, allowing an attacker to overflow the stack buffer. This memory corruption can lead to arbitrary code execution with the privileges of the httpd process, potentially allowing full compromise of the device. The attack vector is remote and requires no authentication or user interaction, making it highly exploitable. The vulnerability has been publicly disclosed, and although no confirmed exploits are currently active in the wild, the availability of exploit code increases the risk of imminent attacks. The CVSS 4.0 base score of 9.3 reflects the critical nature of this vulnerability, with high impact on confidentiality, integrity, and availability, and an attack complexity rated as low. The vulnerability affects a specific firmware version, so devices running this version or earlier are vulnerable. Given the role of routers in network infrastructure, exploitation could lead to network disruption, interception of sensitive data, or pivoting into internal networks.

For European organizations, this vulnerability poses a significant risk to network security and operational continuity. Compromise of Tenda W6-S routers could allow attackers to intercept, modify, or redirect network traffic, leading to data breaches or espionage. Critical infrastructure, SMEs, and enterprises relying on these devices for internet connectivity or internal segmentation could face service outages or unauthorized access. The ability to execute arbitrary code remotely without authentication increases the likelihood of automated attacks and wormable exploits. This could also facilitate lateral movement within corporate networks, impacting confidentiality and integrity of sensitive information. The disruption of availability could affect business operations, especially in sectors like finance, healthcare, and government services. The public disclosure of the vulnerability and exploit code elevates the urgency for mitigation to prevent exploitation in European networks.

Immediate mitigation should focus on obtaining and applying official firmware updates from Tenda that address CVE-2025-15255. If patches are not yet available, organizations should implement network-level protections such as web application firewalls (WAFs) or intrusion prevention systems (IPS) configured to detect and block malformed HTTP Cookie headers targeting the vulnerable component. Network segmentation should isolate vulnerable devices from critical assets. Administrators should disable remote management interfaces on Tenda W6-S devices or restrict access to trusted IP addresses. Regular monitoring of network traffic for anomalous HTTP requests and logs from the router should be conducted to detect exploitation attempts. Additionally, organizations should inventory all Tenda W6-S devices to identify and prioritize patching. Vendor engagement is recommended to obtain timely patches and guidance. Finally, consider replacing vulnerable devices with models from vendors with stronger security track records if updates are delayed.