CVE-2026-1548 identifies a command injection vulnerability in the Totolink A7000R router firmware version 4.1cu.4154. The vulnerability resides in the CloudACMunualUpdateUserdata function of the /cgi-bin/cstecgi.cgi endpoint. Specifically, the 'url' parameter is improperly sanitized, allowing an attacker to inject arbitrary system commands. Because the endpoint is accessible remotely and does not require authentication or user interaction, an attacker can exploit this flaw over the network to execute commands with the privileges of the web server process, which often runs with elevated rights on embedded devices. This can lead to full compromise of the router, enabling attackers to modify device configurations, intercept or redirect network traffic, deploy malware, or use the device as a foothold for further attacks within the network. The vulnerability has a CVSS 4.0 base score of 5.3, reflecting medium severity due to the requirement of limited privileges (PR:L) but no user interaction or authentication. Although no active exploitation has been reported, the availability of exploit code increases the risk of future attacks. The lack of official patches or mitigation guidance at the time of publication necessitates immediate defensive measures by affected users.

For European organizations, this vulnerability poses a significant risk to network security and operational continuity. Compromise of Totolink A7000R routers could lead to unauthorized access to internal networks, interception of sensitive communications, and disruption of internet connectivity. This is particularly critical for small and medium enterprises or branch offices that rely on these routers as primary network gateways without additional layers of security. Attackers could leverage the vulnerability to establish persistent access, launch lateral movement, or exfiltrate data. Given the remote exploitability without authentication, attackers can target exposed devices directly from the internet or through compromised internal hosts. The medium severity rating suggests moderate impact, but the actual damage could escalate depending on the attacker's objectives and network architecture. European organizations with limited network segmentation or outdated device inventories are at heightened risk.

1. Immediately identify and inventory all Totolink A7000R devices running firmware version 4.1cu.4154 within the network. 2. Restrict remote access to the router management interface by implementing firewall rules that limit access to trusted IP addresses or VPN connections only. 3. Disable or restrict access to the vulnerable /cgi-bin/cstecgi.cgi endpoint if possible, through device configuration or network-level controls. 4. Monitor network traffic for unusual requests targeting the CloudACMunualUpdateUserdata function or suspicious command execution patterns. 5. Employ network segmentation to isolate vulnerable devices from critical infrastructure and sensitive data stores. 6. Regularly update router firmware when vendor patches become available; if no patch exists, consider replacing affected devices with models from vendors with active security support. 7. Implement intrusion detection systems (IDS) tuned to detect command injection attempts and anomalous router behavior. 8. Educate IT staff about this vulnerability and ensure incident response plans include steps for compromised network devices. 9. Where feasible, use multi-factor authentication and strong credentials for device management to reduce risk of unauthorized access.