CVE-2026-27512 is a vulnerability classified under CWE-79 (Improper Neutralization of Input During Web Page Generation, i.e., Cross-site Scripting) and CWE-116 (Improper Encoding or Escaping of Output). It affects the administrative interface of the Shenzhen Tenda F3 wireless router firmware version V12.01.01.55_multi. The core issue stems from the router's HTTP responses omitting the security header X-Content-Type-Options: nosniff, which instructs browsers not to perform MIME sniffing. Without this header, certain browsers may interpret the response content type incorrectly, especially when attacker-controlled input is reflected in the response body. This content-type confusion can cause the browser to treat the response as active HTML, allowing injected scripts to execute in the context of the router's administrative interface. The vulnerability does not require any privileges or authentication to exploit but does require user interaction, such as an administrator clicking a malicious link. The CVSS 4.0 vector indicates network attack vector (AV:N), low attack complexity (AC:L), no privileges required (PR:N), user interaction required (UI:A), and limited scope and impact on confidentiality, integrity, and availability. No patches or known exploits have been reported yet. The vulnerability highlights a common web security misconfiguration that can lead to XSS attacks, potentially compromising router administration sessions or enabling further attacks within the network.

The primary impact of CVE-2026-27512 is the potential for an attacker to execute arbitrary scripts within the administrative interface of the affected Tenda F3 routers. This can lead to session hijacking, unauthorized configuration changes, or the injection of malicious payloads that compromise the router's integrity and the security of the internal network. Since the router often serves as a gateway device, compromise can facilitate lateral movement, data interception, or persistent network access. The requirement for user interaction (an admin visiting a malicious link) limits mass exploitation but targeted attacks against network administrators or users with access to the router's interface are feasible. The absence of the X-Content-Type-Options header is a misconfiguration that increases risk, especially in environments where administrators may access the router interface from browsers susceptible to MIME sniffing. Organizations relying on Tenda F3 routers may face increased risk of network compromise, data leakage, or service disruption if this vulnerability is exploited.

1. Immediate mitigation should include restricting administrative interface access to trusted networks or VPNs to reduce exposure to untrusted users. 2. Administrators should avoid accessing the router interface from browsers known to be vulnerable to MIME sniffing or ensure browser security settings are hardened. 3. Implement network-level protections such as web application firewalls (WAFs) or intrusion detection systems (IDS) to detect and block suspicious requests targeting the router's admin interface. 4. Monitor router logs for unusual access patterns or unexpected administrative changes. 5. Contact Shenzhen Tenda Technology Co., Ltd. for firmware updates or patches addressing this vulnerability and apply them promptly once available. 6. As a longer-term measure, consider deploying routers from vendors with stronger security postures and regularly review device configurations to enforce security headers like X-Content-Type-Options. 7. Educate network administrators about phishing and social engineering risks that could lead to user interaction exploitation.