Tenda F456 EUVD-2026-25800

Authentication required - attacker must have valid credentials to the Tenda F456 web management interface (CVSS PR:L). The /goform/Natlimit endpoint is part of the administrative interface, typically accessible only to logged-in users with router admin privileges. Exploitation requires the web management interface to be network-accessible from the attacker's position, either via WAN if remote management is enabled (common misconfiguration) or from LAN for insider threats. Default Tenda credentials (admin/admin) are widely documented and frequently unchanged in home deployments, effectively lowering the authentication barrier. No special firmware feature toggles or non-default configurations are mentioned in the vulnerability description - this affects standard installations of firmware version 1.0.0.5. Attack surface is limited by authentication requirement but expanded by prevalence of weak/default passwords on consumer routers.

CVSS 7.4 (High) reflects network-accessible exploitation with high confidentiality, integrity, and availability impact. CVSS 4.0 vector shows AV:N/AC:L/PR:L (network attack, low complexity, low privileges required) with E:P (POC exists). The requirement for PR:L (authentication) significantly reduces mass exploitation risk compared to unauthenticated flaws - attackers need valid router credentials first. However, SOHO routers commonly use default passwords ('admin/admin'), making credential acquisition trivial in many deployments. The published GitHub POC demonstrates weaponizability, but no CISA KEV listing suggests targeted rather than widespread exploitation. Primary risk is to home/small office networks with default credentials or weak password policies. Enterprise networks rarely deploy Tenda consumer routers, limiting organizational exposure. Attack complexity is low but authentication prerequisite prevents worm-like propagation.

An attacker scans for Tenda F456 routers with internet-exposed management interfaces (commonly TCP 80/443 or non-standard ports). After identifying vulnerable devices via banner grabbing or fingerprinting the Tenda web interface, the attacker attempts default credentials (admin/admin) or credential stuffing attacks. Once authenticated with low-privilege credentials (PR:L), the attacker sends a specially crafted HTTP POST request to /goform/Natlimit with oversized parameters, triggering the buffer overflow in the fromNatlimit function. Using techniques demonstrated in the published POC, the attacker overwrites return addresses or function pointers to redirect execution flow, achieving arbitrary code execution with httpd process privileges (typically root on embedded systems). This enables full device compromise, including firmware implant installation, DNS hijacking for man-in-the-middle attacks, or botnet recruitment.