CVE-2026-59800 in 9Router
Summary
by MITRE • 07/07/2026
9Router before 0.4.44 contains an OS command injection vulnerability in the unauthenticated POST /api/tunnel/tailscale-install endpoint (this route is not covered by the dashboard middleware matcher, so no authorization check is applied). The sudoPassword field from the request body is written to the stdin of a 'sudo -S sh' child process. When sudo does not prompt for a password (the process runs as root, NOPASSWD is configured, or a recent sudo timestamp cache exists), the sudoPassword value is interpreted by sh as a shell command, allowing a remote unauthenticated attacker to execute arbitrary OS commands. Exploitation evidence was first observed by the Shadowserver Foundation on 2026-07-04 (UTC).
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Analysis
by VulDB Data Team • 07/07/2026
This vulnerability represents a critical operating system command injection flaw in the 9Router software version 0.4.44 and earlier, where an unauthenticated attacker can execute arbitrary commands on the affected system. The vulnerability specifically resides in the POST /api/tunnel/tailscale-install endpoint which lacks proper authentication checks due to being excluded from the dashboard middleware authorization layer. The flaw occurs when the sudoPassword field from the request payload is directly piped to the stdin of a sudo -S sh child process, creating a dangerous execution chain that bypasses normal security controls.
The technical implementation of this vulnerability leverages the sudo command's -S flag which reads passwords from standard input, combined with the system's NOPASSWD configuration or recent timestamp cache mechanisms. When these conditions are met, the sudoPassword value gets interpreted by the shell as actual command input rather than a password, enabling full command injection capabilities. This allows attackers to execute any arbitrary commands with root privileges, effectively compromising the entire system and potentially enabling lateral movement within network infrastructure.
The operational impact of this vulnerability is severe as it provides remote unauthenticated access to systems running vulnerable 9Router versions, making it particularly dangerous for internet-facing devices. Attackers can leverage this flaw to install malware, establish persistent backdoors, exfiltrate sensitive data, or use the compromised system as a launch point for further attacks against internal networks. The vulnerability's discovery by Shadowserver Foundation on 2026-07-04 indicates active exploitation in the wild, with potential for widespread compromise across affected deployments.
Security mitigations should focus on immediate patching to version 0.4.44 or later where this vulnerability has been addressed. Organizations must also implement network segmentation to limit exposure of vulnerable systems, disable unnecessary API endpoints, and ensure proper authorization controls are applied consistently across all application routes. The vulnerability aligns with CWE-78 OS Command Injection and maps to ATT&CK technique T1059.004 for command and script injection, representing a significant risk that requires immediate remediation as per industry best practices for protecting industrial control systems and network infrastructure components.
This flaw demonstrates the critical importance of proper input validation and authentication controls in web applications, particularly in embedded systems where privileged access can lead to complete system compromise. The vulnerability's characteristics align with common attack patterns targeting IoT and networking equipment where default configurations may include NOPASSWD settings that create dangerous execution paths when combined with insufficient input sanitization.