CVE-2026-30140: Tenda W15E Information Disclosure Flaw

CVE-2026-30140 Overview

An incorrect access control vulnerability has been identified in the Tenda W15E router firmware version V02.03.01.26_cn. This vulnerability allows unauthenticated remote attackers to access the /cgi-bin/DownloadCfg/RouterCfm.jpg endpoint to download the device's configuration file, which contains plaintext administrator credentials. Successful exploitation leads to sensitive information disclosure and potentially enables remote administrative access to the affected device.

Critical Impact

Unauthenticated attackers can retrieve plaintext administrator credentials from the router configuration file, enabling complete device compromise and network-level access.

Affected Products

• Tenda W15E V02.03.01.26_cn

Discovery Timeline

• 2026-03-09 - CVE-2026-30140 published to NVD
• 2026-03-11 - Last updated in NVD database

Technical Details for CVE-2026-30140

Vulnerability Analysis

This vulnerability stems from an incorrect access control implementation (CWE-284) in the Tenda W15E router's web management interface. The affected endpoint /cgi-bin/DownloadCfg/RouterCfm.jpg lacks proper authentication checks, allowing any remote attacker with network access to retrieve the router's configuration backup file without providing credentials.

The disguised file extension .jpg suggests an attempt to obscure the configuration download functionality, but this security-through-obscurity approach fails to provide any actual protection. The configuration file contains sensitive data including administrator usernames and passwords stored in plaintext format, creating a direct path to full device compromise.

Root Cause

The root cause of this vulnerability is the absence of authentication verification on the configuration file download endpoint. The web server processes requests to /cgi-bin/DownloadCfg/RouterCfm.jpg without validating that the requesting user has authenticated to the device's administrative interface. Additionally, storing administrator credentials in plaintext within the configuration file compounds the security risk, as any successful configuration file retrieval immediately yields usable credentials.

Attack Vector

The attack vector is network-based and requires no authentication or user interaction. An attacker with network connectivity to the router's management interface can directly request the vulnerable endpoint using standard HTTP methods. The attack sequence is straightforward:

1. The attacker identifies a Tenda W15E router on the network
2. A direct HTTP GET request is made to the /cgi-bin/DownloadCfg/RouterCfm.jpg endpoint
3. The router returns the configuration file without requiring authentication
4. The attacker extracts plaintext administrator credentials from the downloaded file
5. Using the retrieved credentials, the attacker gains full administrative access to the router

This vulnerability can be exploited from any network segment with access to the router's web management interface, including the LAN, and potentially from the WAN if remote management is enabled.

Detection Methods for CVE-2026-30140

Indicators of Compromise

• Unexpected HTTP requests to /cgi-bin/DownloadCfg/RouterCfm.jpg endpoint in router logs
• Successful authentication events from unknown IP addresses following configuration file downloads
• Network traffic containing configuration file data being exfiltrated
• Unauthorized changes to router configuration or credentials

Detection Strategies

• Monitor web server access logs for requests to the /cgi-bin/DownloadCfg/ directory from non-administrative sources
• Implement network intrusion detection rules to alert on HTTP responses containing configuration file patterns from Tenda devices
• Deploy network monitoring to detect unusual outbound data transfers from router IP addresses
• Correlate administrative login events with prior configuration download requests to identify potential credential theft

Monitoring Recommendations

• Enable and regularly review router access logs for suspicious endpoint access patterns
• Implement network segmentation to restrict management interface access to trusted administrative networks only
• Deploy SIEM rules to correlate configuration download attempts with subsequent authentication events
• Establish baseline traffic patterns for router management interfaces to detect anomalous access

How to Mitigate CVE-2026-30140

Immediate Actions Required

• Restrict network access to the router's web management interface using firewall rules or access control lists
• Disable remote management functionality if not required for operations
• Isolate affected devices on a dedicated management VLAN accessible only to authorized administrators
• Change administrator credentials immediately and monitor for unauthorized access
• Consider replacing the affected device with a supported alternative if no patch is available

Patch Information

At the time of publication, no official patch information has been released by Tenda for this vulnerability. Organizations should monitor GitHub CVE Report for Tenda Router and the vendor's official channels for firmware updates addressing this issue.

Workarounds

• Implement strict network access controls to limit management interface access to trusted IP addresses only
• Disable the web management interface entirely if configuration changes can be made via alternative methods
• Place affected routers behind a firewall that blocks access to the /cgi-bin/DownloadCfg/ path from untrusted networks
• Use VPN or jump host architecture to access router management interfaces rather than direct network exposure

Network administrators should implement firewall rules to restrict access to the vulnerable endpoint. For example, on perimeter firewalls or internal security devices, block external access to the router's management ports (typically TCP/80 and TCP/443) and ensure only authorized management workstations can reach the device's web interface.