The Critical Cisco IOS XE WLC Flaw: CVE-2025-20188 Explained
A newly disclosed vulnerability, CVE-2025-20188, in Cisco’s IOS XE software for Wireless LAN Controllers poses significant risks to network security. Detailed by Horizon3 researchers, this flaw allows remote attackers to upload arbitrary files and execute commands, threatening the integrity of affected devices. Learn about the nature of this vulnerability, its impact, and proactive measures to safeguard your network.
Understanding the Cisco IOS XE WLC Vulnerability
On May 7, 2025, Cisco revealed a critical security flaw within its IOS XE software. This vulnerability, originating from a hard-coded JSON Web Token (JWT), permits unauthenticated, remote attackers to exploit affected devices if the ‘Out-of-Band AP Image Download’ feature is enabled. Vulnerable 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
How the Flaw Works
The inherent weakness lies in the use of a fallback secret string “notfound” utilized by backend Lua scripts intended for file uploads. When the ‘/tmp/nginx_jwt_key’ file is absent, the system resorts to this fallback, enabling attackers to generate valid JWT tokens effortlessly. By employing the ‘HS256’ signing algorithm, malicious entities can craft legitimate tokens with minimal effort.
Horizon3 provided a demonstration where the attacker executes an HTTP POST request to the ‘/ap_spec_rec/upload/’ endpoint on port 8443, using filename path traversal to drop a harmless file (e.g., foo.txt) outside its designated directory.
Escalation to Remote Code Execution
The gravity of this vulnerability escalates as attackers can trigger remote code execution. By overwriting essential configuration files used by backend services, they can introduce web shells or exploit monitored files to instigate unauthorized actions. In Horizon3’s examination, they demonstrated how to leverage the ‘pvp.sh’ service to alter config files and compel a reload that executes attacker-specified commands.
Mitigation Strategies
Given the immediate threat of exploitation, it is crucial for users to upgrade to a patched software version (17.12.04 or newer) without delay. A temporary workaround involves disabling the ‘Out-of-Band AP Image Download’ feature, thereby closing off the vulnerable service.
Frequently Asked Questions
Question 1: What is CVE-2025-20188?
Answer: CVE-2025-20188 is a high-severity vulnerability in Cisco’s IOS XE software that allows attackers to exploit devices by uploading arbitrary files and executing remote commands due to a hard-coded JWT issue.
Question 2: Who is affected by this vulnerability?
Answer: Users of specific Cisco models, including Catalyst 9800 series wireless controllers, are at risk, especially when the ‘Out-of-Band AP Image Download’ feature is enabled.
Question 3: What should I do if I am affected?
Answer: It is recommended that you upgrade to the latest patched version (17.12.04 or newer) immediately. As a temporary measure, disable the ‘Out-of-Band AP Image Download’ feature to mitigate risks.
Unique Tip for Cyber Security
Implementing a rigorous incident response plan is essential for organizations, especially those prone to file upload vulnerabilities. Regular security assessments and the use of automated patch management tools can significantly reduce risks associated with outdated software and potential exploits.