CVE-2025-11666 is a vulnerability identified in the Tenda RP3 Pro router series firmware up to version 22.5.7.93. The flaw resides in the force_upgrade.sh script, part of the Firmware Update Handler, where a hard-coded password is used. Specifically, manipulation of the argument current_force_upgrade_pwd allows an attacker with local access to bypass authentication controls by leveraging this hard-coded password. This can enable unauthorized firmware upgrade operations, potentially allowing an attacker to install malicious firmware or alter device functionality. The attack vector is local, meaning the attacker must have access to the device's internal network or physical access. The CVSS 4.0 score is 8.4 (high severity), reflecting the significant impact on confidentiality, integrity, and availability, combined with low attack complexity and no user interaction required. The vulnerability requires high privileges locally but no authentication bypass beyond the hard-coded password. Although no known exploits are currently active in the wild, the public availability of exploit code increases the likelihood of future attacks. The absence of official patches or updates at this time necessitates immediate risk mitigation by affected users. This vulnerability poses a serious risk as it could allow attackers to compromise the device firmware, leading to persistent backdoors, network traffic interception, or denial of service.

For European organizations, this vulnerability could lead to severe security breaches if attackers gain local access to Tenda RP3 Pro routers. Compromise of these devices can result in unauthorized firmware modifications, enabling persistent malware installation, interception or manipulation of network traffic, and potential lateral movement within corporate networks. This threatens the confidentiality of sensitive data, the integrity of network communications, and the availability of critical network infrastructure. Given the widespread use of Tenda routers in small to medium enterprises and home office environments across Europe, exploitation could facilitate entry points for broader attacks. Critical sectors such as finance, healthcare, and government agencies relying on these devices for network connectivity may face increased risk of espionage or disruption. The local access requirement somewhat limits remote exploitation but insider threats or compromised internal devices could leverage this vulnerability. The published exploit code further elevates the risk of exploitation, especially in environments with weak internal network segmentation or inadequate physical security.

Since no official patches or firmware updates are currently available, European organizations should implement immediate compensating controls. These include restricting physical and local network access to Tenda RP3 Pro devices, enforcing strict network segmentation to isolate vulnerable routers from critical systems, and monitoring for unusual firmware upgrade attempts or device behavior. Administrators should disable or restrict access to the Firmware Update Handler component if possible, or replace affected devices with models from vendors with timely security support. Employing network intrusion detection systems (NIDS) to detect anomalous upgrade commands or unauthorized access attempts can provide early warning. Regularly auditing device configurations and access logs is essential to identify potential exploitation. Organizations should also educate staff about the risks of local device access and enforce strong internal security policies. Once Tenda releases a patch, immediate firmware upgrade is critical. Until then, consider deploying endpoint security solutions that can detect lateral movement or exploitation attempts originating from compromised routers.