CVE-2026-1548 is a command injection vulnerability identified in the Totolink A7000R router firmware version 4.1cu.4154. The vulnerability resides in the CloudACMunualUpdateUserdata function within the /cgi-bin/cstecgi.cgi script. An attacker can manipulate the 'url' parameter passed to this function to inject and execute arbitrary system commands remotely. This flaw arises due to insufficient input validation or sanitization of the 'url' argument, allowing shell commands to be injected and executed with the privileges of the web server process, which typically runs with elevated permissions on the router. The attack vector is network-based and does not require authentication or user interaction, making it accessible to remote attackers scanning for vulnerable devices. The CVSS 4.0 vector indicates low complexity (AC:L), no privileges required (PR:L but no authentication needed), and no user interaction (UI:N), with partial impact on confidentiality, integrity, and availability. Although no confirmed exploitation in the wild has been reported, the publication of proof-of-concept exploits increases the likelihood of active attacks. Successful exploitation could allow attackers to gain control over the router, modify configurations, disrupt network traffic, or pivot to internal networks. The lack of available patches or official vendor mitigation at the time of disclosure necessitates immediate defensive actions by users and administrators.

For European organizations, exploitation of this vulnerability could lead to significant network security risks. Compromise of the Totolink A7000R routers could allow attackers to intercept, modify, or disrupt network traffic, potentially affecting business operations and data confidentiality. Attackers could use compromised routers as footholds to launch further attacks within corporate networks or to exfiltrate sensitive information. The availability of the network could be impacted through denial-of-service conditions induced by malicious commands. Given the remote and unauthenticated nature of the exploit, attackers can target exposed devices over the internet or internal networks without needing credentials, increasing the attack surface. Organizations relying on these routers for critical infrastructure or remote office connectivity face heightened risks of operational disruption and data breaches. The medium CVSS score reflects moderate risk but should be treated seriously due to the ease of exploitation and potential for lateral movement within networks.

1. Immediately disable remote management interfaces on Totolink A7000R devices to reduce exposure. 2. Restrict access to the /cgi-bin/cstecgi.cgi endpoint via firewall rules or network segmentation to trusted IP addresses only. 3. Monitor network traffic for unusual requests targeting the CloudACMunualUpdateUserdata function or suspicious command injection patterns. 4. If possible, downgrade or upgrade firmware to a version not affected by this vulnerability once a patch is released by the vendor. 5. Employ network intrusion detection/prevention systems (IDS/IPS) with signatures for this vulnerability or generic command injection attempts. 6. Conduct regular audits of router configurations and logs to detect unauthorized changes or access attempts. 7. Educate IT staff on the risks of command injection and the importance of timely patching and configuration management. 8. Consider replacing vulnerable devices with models from vendors with stronger security track records if patches are unavailable or delayed.