Critical Cisco IOS XE Flaw Permits Arbitrary File Upload — PoC Released

A critical security vulnerability, tracked as CVE-2025-20188, has been discovered in Cisco IOS XE Wireless LAN Controllers (WLCs), threatening enterprise wireless infrastructures worldwide.

This flaw, scoring a maximum 10.0 on the CVSS scale, allows unauthenticated remote attackers to upload arbitrary files and potentially execute commands as root, granting full control over affected devices.

The vulnerability arises from a hard-coded JSON Web Token (JWT) used in the Out-of-Band AP (Access Point) Image Download feature of Cisco IOS XE Software for WLCs.

When this feature is enabled, attackers can exploit the flaw via crafted HTTPS requests, bypassing authentication and uploading files to sensitive locations on the device filesystem.

This includes the possibility of path traversal, enabling attackers to overwrite configuration files or plant malicious scripts for remote code execution (RCE).

Key Technical Details

• Vulnerable Component: Out-of-Band AP Image Download feature
• Authentication Bypass: Hard-coded JWT in Lua scripts (ewlc_jwt_verify.lua, ewlc_jwt_upload_files.lua)
• Exploitation Method: Crafted HTTPS POST requests to upload arbitrary files
• Potential Impact: Path traversal, arbitrary file write, root-level command execution

Example Nginx Configuration Block

textlocation /aparchive/upload {
    access_by_lua_file /var/scripts/lua/features/ewlc_jwt_verify.lua;
    content_by_lua_file /var/scripts/lua/features/ewlc_jwt_upload_files.lua;
    client_max_body_size 1536M;
    set $upload_file_dst_path "/bootflash/completeCDB/";
}

Attackers can exploit the upload endpoint by manipulating the filename parameter for path traversal, such as filename="../../usr/binos/openresty/nginx/html/foo.txt", to place files in web-accessible or system-critical directories1.

Affected Products and Exploitation Conditions

The vulnerability affects several Cisco WLC models running IOS XE with the Out-of-Band AP Image Download feature enabled.

Notably, this feature is not enabled by default, but may be active in some deployments or enabled inadvertently during configuration.

Product Name	Conditions for Vulnerability	Associated CVE
Catalyst 9800-CL Wireless Controllers for Cloud	IOS XE WLC, Feature Enabled	CVE-2025-20188
Catalyst 9800 Embedded Wireless Controller (9300/9400/9500)	IOS XE WLC, Feature Enabled	CVE-2025-20188
Catalyst 9800 Series Wireless Controllers	IOS XE WLC, Feature Enabled	CVE-2025-20188
Embedded Wireless Controller on Catalyst APs	IOS XE WLC, Feature Enabled	CVE-2025-20188

Non-affected products include Cisco IOS, IOS XR, Meraki, NX-OS, and AireOS platforms.

Mitigation, Detection, and Recommendations

Cisco has released patched software to remediate the vulnerability.

Administrators are strongly urged to upgrade to the latest fixed versions immediately.

If the immediate upgrade is not feasible, disabling the Out-of-Band AP Image Download feature is advised as a temporary mitigation.

With this feature disabled, AP image updates revert to the more secure CAPWAP method, which does not expose the vulnerable endpoints.

Mitigation Steps:

• Upgrade to the latest Cisco IOS XE WLC software release
• Disable Out-of-Band AP Image Download feature:
  • Navigate to Configuration → Wireless Global → AP Image Upgrade section
  • Ensure the feature is set to disabled

Detection:

• Monitor for unexpected file uploads or changes in system directories
• Audit WLC configurations for the status of the Out-of-Band AP Image Download feature

Security Advisory Table

Mitigation Action	Description
Software Update	Apply Cisco’s latest security patches
Feature Disablement	Turn off Out-of-Band AP Image Download
Network Monitoring	Watch for suspicious upload activity
Configuration Audit	Confirm feature status and restrict access

CVE-2025-20188 underscores the risks of hard-coded credentials and insufficient input validation in critical infrastructure.

Enterprises relying on Cisco IOS XE WLCs must act swiftly to patch or mitigate this flaw, as exploitation could result in full compromise of wireless network controllers and, by extension, all connected clients and devices.

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