CVE-2025-20375: Cisco Unified CCX RCE Vulnerability

CVE-2025-20375 Overview

CVE-2025-20375 is an unrestricted file upload vulnerability [CWE-434] in the web UI of Cisco Unified Contact Center Express (Unified CCX). An authenticated remote attacker with administrative credentials can upload and execute arbitrary files on a vulnerable system. Successful exploitation grants access to the underlying operating system. The flaw stems from insufficient input validation in specific web UI features. Cisco published a security advisory tracking this issue alongside related vulnerabilities in the Unified CCX product line.

Critical Impact
An authenticated administrator can upload crafted files through the web UI, execute them on the host, and gain full operating system access on the affected Cisco Unified CCX server.

Affected Products

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

Discovery Timeline

2025-11-05 - CVE-2025-20375 published to NVD
2025-11-17 - Last updated in NVD database

Technical Details for CVE-2025-20375

Vulnerability Analysis

The vulnerability resides in file upload handlers exposed through the Unified CCX web UI. The application accepts files from authenticated administrators but fails to validate file type, content, or destination path with sufficient rigor. An attacker can submit a crafted file that the server stores in a location reachable by its execution context. The attacker then triggers the file, and the host executes it under the privileges of the Unified CCX service. The result is arbitrary code execution on the underlying operating system, including the ability to pivot, persist, or extract contact center data.

Because Unified CCX integrates with telephony, agent desktops, and customer interaction records, post-exploitation impact extends beyond the host. The attack requires valid administrative credentials, so credential theft, reused passwords, or insider misuse become the primary preconditions for exploitation.

Root Cause

The root cause is improper input validation on file uploads, classified as [CWE-434] Unrestricted Upload of File with Dangerous Type. The web UI logic does not enforce a strict allow-list of permitted file types, validate magic bytes, or restrict the upload directory to a non-executable path. This combination converts a routine administrative feature into a remote code execution primitive.

Attack Vector

The attack vector is network-based over the Unified CCX web UI, typically HTTPS. The attacker authenticates with administrator credentials, navigates to a vulnerable upload feature, and submits a crafted payload such as a server-side script or executable. After upload, the attacker requests the file or invokes the corresponding handler to execute it. No user interaction is required beyond the attacker's own session.

No public proof-of-concept exploit code is currently available. See the Cisco Security Advisory for vendor-confirmed technical details.

Detection Methods for CVE-2025-20375

Indicators of Compromise

Unexpected files written to Unified CCX web application directories, particularly executable or script files outside known upload paths.
Web server access logs showing POST requests to administrative upload endpoints followed by GET requests to newly created files.
New child processes spawned by the Unified CCX web service process that do not match baseline behavior.
Outbound network connections from the Unified CCX host to unfamiliar IP addresses shortly after administrative uploads.

Detection Strategies

Audit administrative login events for the Unified CCX web UI and correlate them with file upload activity.
Monitor file system changes in Unified CCX application directories using integrity monitoring tools.
Inspect HTTP request bodies for non-standard file extensions or executable magic bytes reaching upload endpoints.
Hunt for process lineage where the Unified CCX service spawns shells, interpreters, or system utilities.

Monitoring Recommendations

Forward Unified CCX application, system, and web server logs to a centralized SIEM for correlation.
Alert on administrative authentication from unexpected source addresses or outside change windows.
Track EPSS scoring (currently 0.321%) as a signal for changing exploitation likelihood and adjust monitoring priority accordingly.

How to Mitigate CVE-2025-20375

Immediate Actions Required

Apply the fixed software releases identified in the Cisco Security Advisory for Unified CCX.
Rotate all Unified CCX administrative credentials and enforce multi-factor authentication where supported.
Restrict network access to the Unified CCX web UI to trusted administrative networks only.
Review recent administrative activity and file upload history for signs of prior abuse.

Patch Information

Cisco has released fixed software for Unified Contact Center Express addressing this vulnerability. Refer to the advisory cisco-sa-cc-mult-vuln-gK4TFXSn for the specific fixed release versions and upgrade paths applicable to your deployment. No workaround that fully neutralizes the issue is available from the vendor, so upgrading is the required remediation.

Workarounds

Limit Unified CCX administrative web UI access to dedicated management VLANs or jump hosts.
Enforce least privilege by reducing the number of accounts holding administrator roles.
Place the management interface behind a reverse proxy or web application firewall that restricts file upload content types.
Continuously monitor administrative sessions and file system writes until patching is complete.

bash

# Example: restrict access to the Unified CCX admin UI at the network edge
# Replace the placeholders with your management subnet and CCX host
iptables -A INPUT -p tcp -s 10.10.20.0/24 --dport 443 -d <ccx_host_ip> -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -d <ccx_host_ip> -j DROP