CVE-2024-39781 is a critical command injection vulnerability identified in the Wavlink AC3000 router, firmware version M33A8.V5030.210505. The flaw resides in the adm.cgi script's sch_reboot() function, specifically in the handling of the restart_hour POST parameter. Improper neutralization of special elements (CWE-77) allows an authenticated attacker to inject arbitrary OS commands via a specially crafted HTTP request. This vulnerability enables the attacker to execute commands with the privileges of the web server process, potentially leading to full system compromise including unauthorized access, data exfiltration, or disruption of network services. The CVSS 3.1 base score of 9.1 indicates a critical severity with network attack vector (AV:N), low attack complexity (AC:L), requiring high privileges (PR:H) but no user interaction (UI:N), and impacts confidentiality, integrity, and availability (C:H/I:H/A:H). No public exploits have been reported yet, but the vulnerability’s nature and ease of exploitation make it a high-risk issue. The affected product is primarily used as a wireless router in home and small office environments, but may also be deployed in enterprise edge networks. The vulnerability’s exploitation requires authentication, which somewhat limits remote exploitation but still poses a significant threat if credentials are compromised or weak. The lack of available patches at the time of publication necessitates immediate risk mitigation strategies.

For European organizations, exploitation of this vulnerability could lead to severe consequences including unauthorized control over network infrastructure, interception or manipulation of sensitive data, and disruption of critical network services. Given the critical CVSS score and the ability to execute arbitrary commands, attackers could pivot from compromised routers to internal networks, escalating attacks on corporate or governmental systems. This is particularly concerning for sectors such as finance, healthcare, and critical infrastructure where network reliability and data confidentiality are paramount. The requirement for authentication reduces the risk from purely external attackers but elevates the threat from insider attackers or those who have obtained valid credentials through phishing or other means. The widespread use of Wavlink devices in European small and medium enterprises and some public sector deployments increases the attack surface. Additionally, the vulnerability could be leveraged in botnet formation or as a foothold for ransomware campaigns targeting European networks.

Immediate mitigation should focus on restricting access to the router’s administrative interface to trusted networks and users only, employing strong, unique authentication credentials, and monitoring for suspicious administrative activity. Network segmentation should be enforced to isolate vulnerable devices from critical assets. Since no official patches are currently available, organizations should contact Wavlink support for firmware updates or advisories. If possible, disable the sch_reboot() functionality or any web management features that accept POST requests until a patch is applied. Employ network-level protections such as web application firewalls (WAFs) or intrusion detection/prevention systems (IDS/IPS) to detect and block malicious HTTP requests targeting the vulnerable parameter. Regularly audit router firmware versions and configurations across the organization’s network. Educate users and administrators about the risks of credential compromise and enforce multi-factor authentication (MFA) where supported. Finally, maintain up-to-date backups and incident response plans to minimize impact in case of exploitation.