CVE-2025-20342 Overview
CVE-2025-20342 is a stored cross-site scripting (XSS) vulnerability in the Virtual Keyboard Video Monitor (vKVM) connection handling of Cisco Integrated Management Controller (IMC). The flaw stems from insufficient validation of user-supplied input in the web-based management interface. An authenticated remote attacker with low privileges can inject malicious script into a specific data field. When another user of the interface loads that data, the script executes in their browser context. The affected vKVM client also ships with Cisco UCS Manager, expanding the exposure surface. The vulnerability is tracked under CWE-80 (Improper Neutralization of Script-Related HTML Tags).
Critical Impact
An attacker can execute arbitrary script in the interface context, hijack sessions, or access sensitive browser-based information belonging to legitimate IMC or UCS Manager users.
Affected Products
- Cisco Integrated Management Controller (IMC) — vKVM connection handling component
- Cisco UCS Manager — bundled vKVM client
- Systems exposing the IMC web-based management interface to authenticated users with vKVM privileges
Discovery Timeline
- 2025-08-27 - CVE-2025-20342 published to the National Vulnerability Database
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2025-20342
Vulnerability Analysis
The vulnerability resides in the vKVM connection handling logic within the Cisco IMC web-based management interface. The interface accepts input from authenticated users and stores it without adequate neutralization of HTML or script-related characters. When the interface later renders that stored data to another user, the injected payload executes as active content in the victim's browser session.
Because the payload is stored server-side, exploitation persists across sessions until the malicious data is removed. The scope change reflected in the CVSS metrics indicates that the injected script can affect resources beyond the vulnerable component itself, such as the parent browser origin serving the management console.
User interaction is required. A target user must navigate to the affected interface view to trigger the payload. Successful exploitation yields script execution in the browser context, enabling session token theft, forced actions on behalf of the victim, or exfiltration of data rendered in the management UI.
Root Cause
The root cause is missing or insufficient output encoding and input sanitization on a specific data field handled by the vKVM connection component. Input containing <script> tags, event handlers, or other script-bearing constructs is stored verbatim and later reflected into HTML responses.
Attack Vector
Exploitation requires valid credentials with privileges that permit vKVM access on the target device. The attacker submits a crafted value into the vulnerable field through the web-based management interface. When a legitimate operator subsequently views the affected interface element, the browser parses and executes the injected script.
No verified public exploit code is available. Refer to the Cisco Security Advisory for UCS XSS for vendor-published technical details.
Detection Methods for CVE-2025-20342
Indicators of Compromise
- Unexpected <script> tags, javascript: URIs, or HTML event handler attributes (onerror, onload) stored in vKVM-related configuration fields.
- Outbound HTTP requests from administrator browsers to unknown domains shortly after loading the IMC or UCS Manager interface.
- Anomalous session activity or configuration changes performed under an operator account without corresponding legitimate user actions.
Detection Strategies
- Inspect IMC and UCS Manager audit logs for input modifications to vKVM connection fields by low-privileged accounts.
- Deploy Content Security Policy (CSP) reporting on the management interface to surface script execution violations.
- Correlate administrator browser telemetry with management-plane HTTP requests to identify script-driven, out-of-band actions.
Monitoring Recommendations
- Alert on repeated failed or unusual writes to vKVM-related configuration objects.
- Monitor authentication and session events on IMC and UCS Manager for token reuse from unexpected source addresses.
- Baseline normal administrator browser traffic to management interfaces and flag deviations for review.
How to Mitigate CVE-2025-20342
Immediate Actions Required
- Apply the fixed IMC and UCS Manager releases listed in the Cisco Security Advisory.
- Restrict vKVM privileges to the minimum set of trusted administrators and remove unused accounts.
- Audit existing vKVM-related fields for stored script payloads and sanitize any suspicious content.
Patch Information
Cisco has published fixed software through the security advisory cisco-sa-ucs-kvmsxss-6h7AnUyk. Administrators should consult the advisory to identify the fixed release train for their specific IMC or UCS Manager version and schedule an upgrade. No official workaround is provided by the vendor beyond upgrading to a fixed release.
Workarounds
- Limit network access to the IMC and UCS Manager web interfaces to a dedicated management network or jump hosts.
- Require operators to use isolated browser profiles or dedicated administrative workstations when accessing the management interface.
- Enforce short session timeouts and re-authentication for privileged actions to reduce the exploitation window.
# Configuration example: restrict IMC management access via ACL (illustrative)
# Replace interface and address values to match your environment before applying.
configure terminal
ip access-list extended MGMT-IMC-ACL
permit tcp 10.10.0.0 0.0.0.255 host <imc-mgmt-ip> eq 443
deny ip any host <imc-mgmt-ip> log
permit ip any any
exit
interface <mgmt-interface>
ip access-group MGMT-IMC-ACL in
end
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
