Cisco has disclosed a critical vulnerability affecting Wireless LAN Controllers (WLCs) running IOS XE software. This vulnerability represents one of the most severe security issues discovered in Cisco networking equipment, with the potential to completely compromise the system. The flaw affects organizations worldwide that rely on Cisco wireless infrastructure for their network operations. Given the critical CVSS score of 10.0 and the potential for remote code execution without authentication, this vulnerability constitutes an immediate and significant threat to corporate network security.

The vulnerability is the subject of active research by security teams, and although exploit tools are available, current testing indicates that most production systems have the vulnerable functionality disabled or are running patched versions.

Technical Summary

CVE-2025-20188 is a critical arbitrary file upload vulnerability present in the Out-of-Band Access Point (AP) Image Download functionality of Cisco IOS XE software for Wireless LAN Controllers. The vulnerability stems from the presence of a JSON Web Token (JWT) hard-coded with the secret key “notfound” embedded in the affected systems.

Technical Details:

• Attack Vector: Network-based, does not require authentication
• Affected Component: /ap_spec_rec/upload/ endpoint
• Exploitation Method: Specially crafted HTTPS requests using the hard-coded JWT secret
• Root Cause of Vulnerability: Presence of the hard-coded JWT secret “notfound” allows signature bypass
• Attack Chain:
  1. The attacker creates a malicious JWT using the known secret
  2. Sends a multipart/form-data POST request to the upload endpoint
  3. Exploits path traversal (../../usr/binos/openresty/nginx/html/) to upload files to the web root
  4. Obtains remote code execution with root privileges

Impact Assessment:

• Complete system compromise with root access
• Ability to upload and execute arbitrary files
• Possibility of file system manipulation via path traversal
• Potential for lateral movement within the network infrastructure
• No authentication required for exploitation

Recommendations

1. Apply security patches: Immediately update all Cisco IOS XE WLC systems to the latest patched versions
2. Disable vulnerable functionality: If patching is not immediately possible, disable the Out-of-Band Access Point (AP) Image Download functionality
3. Network segmentation: Isolate WLC systems behind firewalls and restrict access only to essential management traffic
4. Emergency scanning: Deploy the Nuclei template for CVE-2025-20188 to identify vulnerable systems present in the infrastructure