Critical Cisco IOS XE WLC Flaw (CVE-2025-20188) Details Revealed: Urgent Action Required

TL;DR

Details of a critical vulnerability in Cisco IOS XE WLC, tracked as CVE-2025-20188, have been publicly disclosed, heightening the risk of exploitation. This flaw allows unauthenticated, remote attackers to upload arbitrary files and execute commands with root privileges. Affected users are urged to apply software updates and disable the Out-of-Band AP Image Download feature to mitigate risks.

Main Content

Critical Cisco IOS XE WLC Vulnerability (CVE-2025-20188) Details Made Public

Technical details about a critical vulnerability in Cisco IOS XE WLC, identified as CVE-2025-20188, have been publicly disclosed. This disclosure increases the risk of potential exploitation by malicious actors¹.

Understanding the Vulnerability

In early May, Cisco released software updates to address the vulnerability CVE-2025-20188, which has a CVSS score of 10. This flaw allows an unauthenticated, remote attacker to upload arbitrary files to a vulnerable system by sending crafted HTTPS requests to the AP image download interface. Successful exploitation could grant the attacker root access and the ability to execute arbitrary commands².

Advisory Details

According to the Cisco advisory:

A vulnerability in the Out-of-Band Access Point (AP) Image Download feature of Cisco IOS XE Software for Wireless LAN Controllers (WLCs) could allow an unauthenticated, remote attacker to upload arbitrary files to an affected system. This vulnerability is due to the presence of a hard-coded JSON Web Token (JWT) on an affected system. An attacker could exploit this vulnerability by sending crafted HTTPS requests to the AP image download interface. A successful exploit could allow the attacker to upload files, perform path traversal, and execute arbitrary commands with root privileges.

Affected Products

The vulnerability impacts the following products:

• 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

To check if a device is affected, run show running-config | include ap upgrade. If it returns ap upgrade method https, the Out-of-Band AP Image Download feature is enabled.

Mitigation Steps

Cisco states that no workaround exists, but the vulnerability can be mitigated by disabling the Out-of-Band AP Image Download feature. Users are urged to apply the necessary fixes as soon as possible, but they should first assess the impact on their environment.

Discovery and Analysis

Horizon3 researchers discovered the vulnerability and attributed it to a hardcoded fallback secret (“notfound”) and weak path validation. If the system’s JWT key file is missing, it defaults to using “notfound” to verify tokens, making it easy for attackers to create valid tokens without knowing any real secret. By targeting a file upload feature on port 8443, attackers can upload files outside the intended directory, potentially leading to remote code execution by overwriting configuration files or hijacking services³.

Expert Insights

After digging through those services, we discovered an internal process management service (pvp.sh) that waits for files to be written to a specific directory. Once a change is detected, it can trigger a service reload based on the commands specified in the service’s config file.

For remote code execution (RCE), attackers need to:

• Overwrite the existing config file with their own commands.
• Upload a new file to cause the services to be reloaded.
• Check if the exploit succeeded.

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Conclusion

The public disclosure of CVE-2025-20188 highlights the urgent need for affected users to take immediate action. By applying the necessary software updates and disabling the Out-of-Band AP Image Download feature, organizations can significantly reduce the risk of exploitation. Staying informed and proactive is crucial in maintaining robust cybersecurity defenses.

References

1. “Cisco fixed a critical flaw in its IOS XE Wireless Controller” (Security Affairs). Retrieved 2025-06-02. ↩︎

2. “Cisco Security Advisory” (Cisco). Retrieved 2025-06-02. ↩︎

3. “Cisco IOS XE WLC Arbitrary File Upload Vulnerability (CVE-2025-20188) Analysis” (Horizon3). Retrieved 2025-06-02. ↩︎