A critical vulnerability in Cisco IOS XE Wireless LAN Controllers (WLCs), tracked as CVE-2025-20188, is now drawing heightened concern after full technical exploit details were made public. This flaw, originally disclosed on May 7, 2025, carries a maximum CVSS 3.1 score of 10.0 and allows unauthenticated remote attackers to upload arbitrary files and execute code with root privileges.
While no fully weaponized public exploit has yet surfaced, researchers have published detailed technical analysis that significantly lowers the barrier for attackers to develop working exploit code. The combination of public research, ease of exploitation, and the ubiquity of vulnerable devices presents an urgent risk for organizations using affected Cisco hardware.
Technical Details
The vulnerability resides in the Out-of-Band Access Point (AP) Image Download feature of Cisco IOS XE Wireless LAN Controllers. It stems from the use of a hard-coded JSON Web Token (JWT) secret, which can be exploited to bypass authentication entirely.
- The backend OpenResty server (Lua + Nginx) falls back to the static secret value “notfound” when the JWT key file is missing.
- Attackers can generate valid JWT tokens using the HS256 algorithm and the known “notfound” key, granting them unauthorized access.
- This allows file uploads through the vulnerable /ap_spec_rec/upload/ endpoint via HTTPS (port 8443).
- Horizon3 demonstrated the ability to escalate file upload access into full remote code execution by overwriting monitored configuration files and injecting commands that execute with root privileges.
Affected Devices
Only devices with the Out-of-Band AP Image Download feature enabled are vulnerable. Affected models include:
- Catalyst 9800-CL Wireless Controllers for Cloud
- Catalyst 9800 Embedded Wireless Controller for Catalyst 9300, 9400, and 9500 Series Switches
- Catalyst 9800 Series Wireless Controllers
- Embedded Wireless Controller on Catalyst APs
Products confirmed not vulnerable include:
- Cisco IOS XR Software
- Cisco NX-OS Software
- Cisco Meraki products
- AireOS Software
- Cisco IOS XE software running on devices that are not WLCs
Organizations can verify if the vulnerable feature is enabled by running:
show running-config | include ap upgrade
If the output includes ap upgrade method https, the device is vulnerable.
Exploitation Status
As of this writing:
- Public technical details are available and easily leveraged by threat actors.
- No confirmed widespread exploitation reported yet.
- Cisco PSIRT has not observed active malicious use but warns of potential weaponization.
Mitigation & Remediation
Cisco has released fixed software versions; administrators should immediately upgrade to version 17.12.4 or later. For full patching instructions, visit: Cisco Security Advisory
If patching is not available, administrators must disable the Out-of-Band AP Image Download feature to block the vulnerable interface. Cisco has not provided alternative workarounds beyond disabling the feature.
OP Innovate Recommendations
OP Innovate clients are advised to treat CVE-2025-20188 as a high-priority threat and act immediately:
- Inventory all Cisco Catalyst WLCs in your environment.
- Validate current software versions and feature configurations.
- Disable the Out-of-Band AP Image Download feature where immediate patching is not feasible.
- Monitor for unusual traffic on port 8443, file system changes, and unexpected config reload events.
- Prepare for potential exploitation by updating incident response runbooks to include this CVE.
OP Innovate’s Threat Intelligence and Incident Response teams are actively monitoring for potential emergence of weaponized exploit code in underground forums and public repositories, along with signs of initial exploitation attempts in client environments.
