CVE-2025-20376: Cisco Unified CCX RCE Vulnerability

CVE-2025-20376 Overview

CVE-2025-20376 is an arbitrary file upload vulnerability in the web UI of Cisco Unified Contact Center Express (Unified CCX). The flaw stems from insufficient input validation in file upload mechanisms. An authenticated remote attacker with valid administrative credentials can upload a malicious file and execute it on the underlying operating system. Successful exploitation grants arbitrary command execution and privilege escalation to root. Cisco disclosed the issue in security advisory cisco-sa-cc-mult-vuln-gK4TFXSn. The weakness is categorized under [CWE-434: Unrestricted Upload of File with Dangerous Type].

Critical Impact
Authenticated administrators can escalate to root on Cisco Unified CCX appliances by uploading and executing arbitrary files through the web UI.

Affected Products

Cisco Unified Contact Center Express (all versions prior to the fixed release referenced in the advisory)
Cisco Unified Contact Center Express 15.0
Deployments exposing the Unified CCX administrative web UI

Discovery Timeline

2025-11-05 - CVE-2025-20376 published to the National Vulnerability Database
2025-11-17 - Last updated in NVD database

Technical Details for CVE-2025-20376

Vulnerability Analysis

The vulnerability resides in the file upload handler exposed by the Cisco Unified CCX web UI. The handler fails to enforce sufficient validation on uploaded content, allowing an attacker to place executable files into a location the application can later invoke. Once uploaded, the attacker triggers execution of the malicious file through the same web interface. Because the Unified CCX application runs with elevated operating system privileges, command execution escalates to root on the underlying appliance. The issue is tracked as [CWE-434] and requires network reachability to the management interface.

Root Cause

The root cause is improper validation of user-supplied files at upload time. The application does not adequately restrict file type, content, extension, or storage path before accepting the upload. This combination allows arbitrary executable payloads to bypass intended controls and reach a writable, executable location accessible to the web application.

Attack Vector

Exploitation requires valid administrative credentials to the Unified CCX web UI, so the attacker must first authenticate. The attack proceeds over the network against the management interface and requires no user interaction. After authenticating, the attacker submits a crafted file to the vulnerable upload endpoint and then invokes it to obtain command execution as root. Compromised, weak, or shared administrative credentials make this vector practical against exposed appliances.

No public proof-of-concept code is available at the time of writing. Technical specifics are limited to the description in the Cisco Security Advisory.

Detection Methods for CVE-2025-20376

Indicators of Compromise

Unexpected files written to Unified CCX web application directories, particularly executable scripts (.sh, .jsp, .war, or binaries) under upload or temporary paths.
New or unexpected processes spawned by the Unified CCX web service running as root.
Outbound network connections from the Unified CCX appliance to unfamiliar IP addresses following administrative logins.

Detection Strategies

Review Unified CCX administrative audit logs for file upload actions performed by administrator accounts outside of normal change windows.
Monitor authentication logs for administrative logins from unusual source IP addresses or geographies.
Inspect the underlying appliance for child processes of the web application that execute shells, interpreters, or networking utilities.

Monitoring Recommendations

Forward Unified CCX system, audit, and web server logs to a centralized SIEM for correlation with endpoint and network telemetry.
Alert on creation or modification of files within Unified CCX web application directories outside of patch or upgrade activity.
Track administrative session activity and flag uploads followed by immediate HTTP GET requests to the uploaded resource.

How to Mitigate CVE-2025-20376

Immediate Actions Required

Apply the fixed Cisco Unified CCX software release listed in advisory cisco-sa-cc-mult-vuln-gK4TFXSn as soon as possible.
Restrict network access to the Unified CCX administrative web UI to trusted management networks and jump hosts only.
Rotate all administrative credentials and enforce strong, unique passwords on Unified CCX administrator accounts.
Enable multi-factor authentication for administrative access where supported by the deployment.

Patch Information

Cisco has released fixed software versions documented in the Cisco Security Advisory cisco-sa-cc-mult-vuln-gK4TFXSn. Administrators should consult the advisory for the specific fixed release that applies to their Unified CCX version, including the 15.0 train, and plan upgrades accordingly. No workaround fully removes the risk; patching is the recommended remediation.

Workarounds

Limit Unified CCX administrative access through firewall ACLs and VPN-only management until patches are applied.
Review and reduce the number of accounts with administrator privileges on Unified CCX to the minimum required.
Audit existing Unified CCX appliances for unauthorized files or scheduled tasks before and after applying the patch.

bash

# Example: restrict access to the Unified CCX web UI to a management subnet
# (apply on the upstream firewall, not directly on the appliance)
iptables -A INPUT -p tcp --dport 443 -s 10.10.50.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP