CVE-2025-5527 is a critical stack-based buffer overflow vulnerability identified in the Tenda RX3 router firmware version 16.03.13.11_multi_TDE01. The flaw exists in the function save_staticroute_data within the /goform/SetStaticRouteCfg endpoint. This function improperly handles input arguments, allowing an attacker to manipulate the argument list and trigger a stack-based buffer overflow. Because the vulnerability is remotely exploitable without authentication or user interaction, an attacker can send specially crafted requests to the affected router to execute arbitrary code or cause denial of service. The vulnerability has a CVSS 4.0 base score of 8.7 (high severity), reflecting its network attack vector, low attack complexity, no privileges or user interaction required, and high impact on confidentiality, integrity, and availability. Although no public exploits are currently observed in the wild, the public disclosure of the vulnerability increases the risk of exploitation. The vulnerability affects a specific firmware version of the Tenda RX3 router, a consumer and small business networking device commonly used for internet connectivity. The flaw could allow attackers to gain control over the router, intercept or manipulate network traffic, disrupt network availability, or pivot into internal networks, posing significant security risks.

For European organizations, exploitation of CVE-2025-5527 could lead to severe operational and security consequences. Compromised routers could enable attackers to intercept sensitive communications, exfiltrate confidential data, or inject malicious traffic, undermining data confidentiality and integrity. The ability to execute arbitrary code remotely without authentication means attackers could establish persistent footholds within organizational networks, facilitating further lateral movement and advanced persistent threats. Disruption of network availability could impact business continuity, especially for organizations relying on Tenda RX3 routers for critical connectivity. Small and medium enterprises, which often use consumer-grade routers like the Tenda RX3, are particularly at risk. Additionally, the vulnerability could be leveraged in botnet campaigns or distributed denial-of-service (DDoS) attacks, amplifying threats to European internet infrastructure and services.

Organizations should immediately identify any Tenda RX3 devices running firmware version 16.03.13.11_multi_TDE01 and prioritize their remediation. Since no official patches are currently linked, users should monitor Tenda’s official channels for firmware updates addressing this vulnerability and apply them promptly once available. In the interim, network administrators should restrict access to router management interfaces, especially the /goform/SetStaticRouteCfg endpoint, by implementing network segmentation and firewall rules to limit exposure to untrusted networks. Disabling remote management features or restricting them to trusted IP addresses can reduce attack surface. Employing intrusion detection and prevention systems (IDS/IPS) with signatures for buffer overflow attempts targeting Tenda routers can help detect exploitation attempts. Regularly auditing router configurations and monitoring network traffic for anomalies is recommended. Organizations should also consider replacing vulnerable devices with models that have a stronger security track record if timely patches are unavailable.