CVE-2026-7833: EFM ipTIME C200 RCE Vulnerability

CVE-2026-7833 Overview

CVE-2026-7833 is a command injection vulnerability in the EFM ipTIME C200 router through firmware version 1.092. The flaw resides in the sub_408F90 function within /cgi/iux_set.cgi, part of the ApplyRestore Endpoint component. Attackers can manipulate the RestoreFile argument to inject arbitrary operating system commands. The issue is classified under [CWE-74] (Improper Neutralization of Special Elements in Output Used by a Downstream Component). According to the disclosure, a public exploit exists and the vendor did not respond to early disclosure attempts.

Critical Impact
Remote attackers with valid credentials can execute arbitrary commands on affected ipTIME C200 routers, leading to full device compromise and potential pivoting into internal networks.

Affected Products

EFM ipTIME C200 router firmware up to and including version 1.092
The /cgi/iux_set.cgi ApplyRestore Endpoint handler
The sub_408F90 internal function processing the RestoreFile argument

Discovery Timeline

2026-05-05 - CVE-2026-7833 published to NVD
2026-05-05 - Last updated in NVD database

Technical Details for CVE-2026-7833

Vulnerability Analysis

The vulnerability is a classic command injection issue in the firmware's CGI-based configuration handler. When a user invokes the ApplyRestore functionality, the router's web interface posts data to /cgi/iux_set.cgi. The handler routes processing into the sub_408F90 function, which consumes the RestoreFile parameter without sanitizing shell metacharacters. As a result, attacker-supplied content is concatenated into a system command and executed by the underlying shell.

Exploitation requires network access to the device's management interface and authenticated access, as indicated by the high privileges required in the attack vector. Once authenticated, an attacker injects shell separators such as semicolons or backticks into the RestoreFile argument to break out of the intended command context. The injected payload runs with the privileges of the CGI process, typically root on embedded ipTIME devices.

Root Cause

The root cause is missing input neutralization in sub_408F90. The function passes the RestoreFile value into a system-level command invocation without validating the parameter against an allowlist or escaping shell-significant characters. Embedded routers commonly invoke system() or popen() for archive and restore operations, which is the likely sink in this case.

Attack Vector

The attack is launched remotely over the network against the router's HTTP management interface. An authenticated session is required to reach the ApplyRestore handler. After authentication, the attacker submits a crafted multipart or form-encoded request that places shell metacharacters in the RestoreFile field. The injected command executes on the device immediately, returning control of the embedded Linux environment to the attacker.

For technical specifics, refer to the GitHub Vulnerability Report and VulDB #361112.

Detection Methods for CVE-2026-7833

Indicators of Compromise

HTTP POST requests to /cgi/iux_set.cgi containing shell metacharacters such as ;, |, &, backticks, or $() inside the RestoreFile parameter.
Unexpected outbound connections initiated by the router to attacker-controlled hosts following ApplyRestore activity.
New or modified files in writable firmware locations such as /tmp or /var that did not originate from a legitimate firmware update.
Unusual processes spawned by the httpd or CGI parent process on the device.

Detection Strategies

Inspect web server and reverse-proxy logs for requests to iux_set.cgi with non-standard RestoreFile values, especially those exceeding expected length or containing punctuation.
Deploy network IDS signatures that flag command injection patterns in HTTP request bodies destined for ipTIME management interfaces.
Baseline normal administrative activity to the router and alert on ApplyRestore calls from unexpected source addresses or outside maintenance windows.

Monitoring Recommendations

Forward router syslog to a central collector and alert on authentication events followed quickly by configuration restore actions.
Monitor for DNS lookups originating from the router itself, which usually only resolves vendor update endpoints.
Track firmware version inventory across all ipTIME C200 deployments to identify devices still running 1.092 or earlier.

How to Mitigate CVE-2026-7833

Immediate Actions Required

Restrict access to the ipTIME C200 web management interface to a dedicated management VLAN or trusted administrator hosts only.
Disable remote (WAN-side) administration on all affected devices until a vendor patch is verified.
Rotate administrator credentials and remove any default or shared accounts that could be reused to reach the vulnerable endpoint.
Audit recent ApplyRestore activity and configuration backups for signs of tampering.

Patch Information

No vendor patch has been published. EFM was contacted prior to disclosure but did not respond, and no fixed firmware version is available for ipTIME C200 at the time of NVD publication. Organizations should monitor the EFM ipTIME firmware download portal and the VulDB submission record for an updated build.

Workarounds

Place the device behind a network firewall that blocks unsolicited inbound HTTP and HTTPS traffic to the router's management port.
Enforce strong, unique administrator passwords and consider replacing affected ipTIME C200 units with supported hardware if a patch does not arrive.
Use an upstream web application firewall or reverse proxy to drop requests to /cgi/iux_set.cgi containing shell metacharacters in any parameter.

bash

# Example iptables rule to restrict router admin access to a management subnet
iptables -A INPUT -p tcp --dport 80 -s 10.10.0.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -s 10.10.0.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP