CVE-2026-2550: EFM iptime A6004MX Auth Bypass Vulnerability

CVE-2026-2550 Overview

A critical unrestricted file upload vulnerability has been discovered in EFM ipTIME A6004MX router firmware version 14.18.2. The vulnerability exists in the commit_vpncli_file_upload function within the /cgi/timepro.cgi file, allowing remote attackers to upload arbitrary files without proper validation or authentication. This vulnerability could enable complete system compromise of affected network devices.

Critical Impact
Remote attackers can exploit this vulnerability to upload malicious files to the router, potentially leading to remote code execution, persistent backdoor installation, or complete device takeover without any user interaction.

Affected Products

EFM ipTIME A6004MX firmware version 14.18.2
ipTIME A6004MX routers running vulnerable CGI handler

Discovery Timeline

2026-02-16 - CVE-2026-2550 published to NVD
2026-02-18 - Last updated in NVD database

Technical Details for CVE-2026-2550

Vulnerability Analysis

This vulnerability represents an unrestricted file upload flaw (CWE-284: Improper Access Control) in the ipTIME A6004MX router's web management interface. The commit_vpncli_file_upload function within /cgi/timepro.cgi fails to implement proper access controls and file validation, allowing unauthenticated remote attackers to upload arbitrary files to the device.

The attack can be performed remotely over the network without requiring any authentication or user interaction. Once exploited, an attacker could upload malicious scripts or firmware components, potentially achieving persistent access to the network device and all traffic passing through it.

The exploit has been publicly disclosed, and the vendor (EFM) was contacted regarding this vulnerability but did not respond. This lack of vendor acknowledgment increases the risk for organizations using affected devices as no official patch timeline has been established.

Root Cause

The root cause of this vulnerability lies in improper access control implementation within the CGI handler. The commit_vpncli_file_upload function does not adequately verify:

Authentication status of the requesting user
File type restrictions for uploaded content
Upload destination path validation
File content sanitization

This combination of missing security controls allows any remote attacker to directly interact with the file upload functionality without restriction.

Attack Vector

The attack vector for CVE-2026-2550 is network-based, requiring no privileges or user interaction. An attacker can exploit this vulnerability by:

Identifying an exposed ipTIME A6004MX router on the network or internet
Crafting a malicious HTTP request targeting the /cgi/timepro.cgi endpoint
Invoking the commit_vpncli_file_upload function with an arbitrary file payload
Uploading malicious content such as web shells, backdoors, or modified configuration files
Executing the uploaded content to gain persistent access to the device

The vulnerability does not require a valid session or any form of authentication, making it trivially exploitable against any accessible device.

Detection Methods for CVE-2026-2550

Indicators of Compromise

Unusual HTTP POST requests to /cgi/timepro.cgi containing file upload data
Unexpected files appearing in router file system directories
Unauthorized configuration changes or new administrative accounts
Network traffic anomalies originating from the router device
Log entries showing repeated access to the VPN client upload functionality

Detection Strategies

Monitor network traffic for HTTP requests targeting /cgi/timepro.cgi with file upload payloads
Implement IDS/IPS rules to detect exploitation attempts against ipTIME devices
Review router access logs for unauthenticated requests to administrative endpoints
Deploy network monitoring to identify communication patterns indicative of compromised IoT devices

Monitoring Recommendations

Enable comprehensive logging on network perimeter devices for traffic destined to router management interfaces
Implement file integrity monitoring on router firmware and configuration files where supported
Monitor for outbound connections from router devices to unknown external hosts
Establish baseline behavior for router management interface access patterns

How to Mitigate CVE-2026-2550

Immediate Actions Required

Restrict access to the router's web management interface to trusted internal networks only
Implement firewall rules blocking external access to ports 80/443 on the affected device
Monitor for exploitation attempts using network intrusion detection systems
Consider replacing the affected device with a supported alternative if no patch becomes available

Patch Information

No official patch is currently available from the vendor. According to the disclosure, EFM was contacted about this vulnerability but did not respond. Organizations should monitor for firmware updates from ipTIME and apply them immediately when available. Technical details and discussion can be found in the GitHub Issue Discussion and VulDB advisory.

Workarounds

Disable remote management access to the router's web interface entirely
Place the router management interface on an isolated VLAN accessible only to authorized administrators
Implement a VPN requirement for all remote administrative access to the network
Deploy a web application firewall in front of the router management interface to filter malicious requests

bash

# Example firewall rules to restrict access to router management interface
# Block external access to router web interface on port 80
iptables -A INPUT -p tcp --dport 80 -s ! 192.168.1.0/24 -j DROP

# Block external access to router web interface on port 443
iptables -A INPUT -p tcp --dport 443 -s ! 192.168.1.0/24 -j DROP

# Allow only specific admin workstation access
iptables -A INPUT -p tcp --dport 80 -s 192.168.1.100 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -s 192.168.1.100 -j ACCEPT