Command injection enables arbitrary OS command execution on Linksys MR8300 Router

Command injection vulnerability in Linksys MR8300 router while Registration to DDNS Service. By specifying username and password, an attacker connected to the router's web interface can execute arbitrary OS commands. The username and password fields are not sanitized correctly and are used as URL construction arguments, allowing URL redirection to an arbitrary server, downloading an arbitrary script file, and eventually executing the file in the device. This issue affects: Linksys MR8300 Router 1.0.

• Linksys MR8300 Router firmware 1.0 is marked affected in the supplied affected facts and the NVD configuration.
• Linksys release notes cover MR8300 V1 and V1.1 and state that firmware 1.1.10.210186 addressed the command injection vulnerability.
• The available evidence does not verify the status of every later or parallel firmware branch. Do not interpret this fix as an open-ended statement that every newer version is unaffected.

During Registration to DDNS Service, the username and password fields are not sanitized correctly. The values are used as URL construction arguments, which can allow redirection to an arbitrary server, downloading an arbitrary script file, and eventual execution on the device. This is CWE-78, where attacker-controlled input can result in arbitrary operating system command execution. The evidence identifies the web interface and DDNS registration flow but does not identify the endpoint, handler, process identity, or command interpreter involved. The supplied scoring metadata differs on reachability and privilege, so the exact attack boundary remains unresolved.

Reachability is not fully reconciled. The narrative places the attacker at the router's web interface, while the supplied scoring metadata labels the attack vector local and differs on the required privilege level between assessments. The description requires the attacker to submit username and password values but does not describe separate victim interaction. The supplied scoring metadata characterizes attack complexity as low. The record does not establish known exploitation, a public exploit, or ransomware use; the absence of those flags is not proof that exploitation has not occurred.

The technical outcome established by the record is arbitrary OS command execution on the router. If the exploited process has sufficient privileges, an attacker could read or modify configuration, alter runtime state, or disrupt service; these are possible consequences rather than individually confirmed outcomes. One supplied assessment indicates that scope may change, but the record does not explain which security boundary is crossed and does not establish direct access to adjacent systems. The process privilege, persistence behavior, and full impact scope remain unknown.

Successful exploitation can allow arbitrary OS command execution on the router. Depending on the process privileges and the device's network placement, an attacker could read or alter configuration, interfere with management functions, disrupt routing services, or use the router for further activity. The record does not confirm compromise of other hosts, persistence, or a specific breach scenario. Because the router controls network connectivity, affected devices should receive priority in inventory and upgrade work.

1. Inventory Linksys MR8300 devices and identify the firmware currently running, prioritizing devices using firmware 1.0.
2. Upgrade MR8300 to firmware 1.1.10.210186, which Linksys release notes state addressed the command injection vulnerability for MR8300 V1 and V1.1.
3. Until the upgrade can be completed, restrict access to the administrative web interface from untrusted networks where the deployment permits. The supplied evidence does not provide a vendor-confirmed workaround.
4. Follow the vendor's upgrade procedure and do not power down the router during the firmware upgrade process.
5. After upgrading, verify the firmware actually running and review the configuration, DDNS registration activity, and administrative access for anomalies.

• Inventory all Linksys MR8300 devices and their running firmware, prioritizing systems that remain on an affected firmware branch.
• Review router configuration and administrative history for DDNS registration activity, especially unexpected username, password, or destination-server changes.
• Review administrative logs and outbound traffic for connections from the router to unapproved servers after DDNS registration activity. This is precautionary monitoring, not a vendor-confirmed indicator of compromise.
• If suspicious activity is found, isolate the device according to operational procedures, preserve its current configuration and available logs, and verify the firmware after remediation.
• Do not treat the absence of a matching log event as proof of safety; the evidence does not identify a specific log event or IOC.