Technical details revealing how to exploit a maximum-severity vulnerability (CVE-2025-20188) in Cisco IOS XE Wireless LAN Controllers (WLC) have been publicly released, significantly raising the risk of imminent attacks. Horizon3 researchers published a deep dive into the flaw, enabling skilled threat actors—or even advanced AI systems—to weaponize it within hours.

Why This Flaw Is Critical

Disclosed by Cisco on May 7, 2025, this 9.8-CVSS vulnerability allows unauthenticated attackers to upload malicious files, traverse directories, and execute arbitrary commands with root privileges. The attack exploits a hardcoded JSON Web Token (JWT) secret (notfound) used by Cisco’s OpenResty backend when the /tmp/nginx_jwt_key file is missing. Attackers can forge valid tokens to bypass authentication entirely.

Affected Devices:

• Catalyst 9800-CL WLCs (Cloud)
• Catalyst 9800 Embedded WLC (Catalyst 9300/9400/9500 Switches)
• Catalyst 9800 Series WLCs
• Embedded WLC on Catalyst APs

Key Trigger: The ‘Out-of-Band AP Image Download’ feature must be enabled for devices to be vulnerable.

Horizon3’s Weaponization Blueprint

Horizon3’s analysis demonstrates how attackers can:

1. Forge JWT tokens using the hardcoded notfound secret.
2. Upload files via the /ap_spec_rec/upload/ endpoint (port 8443) using path traversal (e.g., ../../).
3. Overwrite critical files (e.g., configs, scripts) to achieve Remote Code Execution (RCE).

In their example, attackers overwrite configurations monitored by the pvp.sh service, triggering a reload to execute malicious payloads with root privileges.

Source: Horizon3 Attack Breakdown

Mitigation Steps: Act Now

Cisco confirms active exploits are expected within days. Take immediate action:

1. PATCH: Upgrade to IOS XE 17.12.04 or later.
2. TEMPORARY FIX: Disable ‘Out-of-Band AP Image Download’ via:

config t > wireless profile ap-download > no out-of-band ap-image-download enable  

The Bottom Line

This flaw transforms a simple file upload into full device takeover. With technical roadmaps now public, unpatched networks face severe ransomware, espionage, and botnet recruitment risks. Cisco administrators must treat this as an emergency patch scenario.

Update Status: Cisco confirms no public exploits yet, but warns weaponization is imminent. Monitor CVE-2025-20188 Bulletin for updates.