CVE-2025-12776: Report Builder Component XSS Vulnerability

CVE-2025-12776 Overview

CVE-2025-12776 is a Stored Cross-Site Scripting (XSS) vulnerability affecting the Report Builder component within the Commvault WebConsole application. The vulnerability occurs because user input is stored directly in a web page without proper validation during report creation, and this input is subsequently displayed to other users. While the malicious scripts are not executed when end users run the report, they are triggered when a user with edit permissions modifies the report through the Report Builder interface.

Critical Impact

This vulnerability allows attackers to inject malicious scripts that execute in the browser context of users with report editing privileges. The WebConsole package containing the vulnerable Report Builder is end-of-life and no longer maintained.

Affected Products

• Commvault WebConsole (End of Life)
• Report Builder component within WebConsole

Discovery Timeline

• 2026-01-07 - CVE CVE-2025-12776 published to NVD
• 2026-01-08 - Last updated in NVD database

Technical Details for CVE-2025-12776

Vulnerability Analysis

This vulnerability is classified as CWE-79 (Improper Neutralization of Input During Web Page Generation), commonly known as Cross-Site Scripting. The flaw exists in the Report Builder component of the Commvault WebConsole application, where user-supplied input is stored without adequate sanitization and later rendered in web pages viewed by other users.

The attack requires authenticated access with the ability to create or modify reports. The stored payload persists in the application and executes when another user with edit permissions accesses the report through the Report Builder interface. This is a stored (persistent) XSS variant, making it potentially more dangerous than reflected XSS as the malicious payload remains in the system until explicitly removed.

The impact is somewhat limited because script execution only occurs for users with edit permissions who access the report through the Report Builder—not when end users simply run the report. However, this still poses risks including session hijacking, credential theft, or privilege abuse within the context of users who have elevated permissions to modify reports.

Root Cause

The root cause of this vulnerability is insufficient input validation and output encoding in the Report Builder component. When users create or modify reports, the application fails to sanitize user-supplied input before storing it in the database. Subsequently, when this content is rendered in the browser for users accessing the Report Builder, the application does not properly encode the output, allowing embedded scripts to execute in the victim's browser context.

Attack Vector

The attack vector is network-based, requiring an authenticated attacker with permissions to create or modify reports in the Report Builder. The attacker crafts a report containing malicious JavaScript code embedded in user-controllable fields. When another user with edit permissions opens this report in the Report Builder interface, the stored malicious script executes in their browser session.

The attack requires user interaction (the victim must access and attempt to edit the poisoned report) and requires the attacker to have high privileges (report creation/editing permissions). This limits the exploitability, but in environments where the WebConsole is still deployed, users with report editing permissions could be targeted for session hijacking or further privilege escalation.

Detection Methods for CVE-2025-12776

Indicators of Compromise

• Unusual or suspicious content within Report Builder reports, particularly fields containing JavaScript or HTML tags
• Reports with encoded script elements such as <script>, javascript:, or event handlers like onerror or onload
• Unexpected modifications to existing reports by users who typically do not edit them

Detection Strategies

• Implement web application firewall (WAF) rules to detect and block XSS patterns in requests to the WebConsole application
• Review application logs for suspicious report creation or modification activities
• Conduct periodic audits of report content for embedded scripts or suspicious HTML elements
• Monitor for unusual session activity from users with report editing privileges

Monitoring Recommendations

• Enable detailed logging for all Report Builder activities including report creation, modification, and access events
• Set up alerts for detection of common XSS payload patterns in application input fields
• Monitor for anomalous user behavior such as accessing reports outside normal working hours or from unusual IP addresses

How to Mitigate CVE-2025-12776

Immediate Actions Required

• Discontinue use of the Commvault WebConsole as it is end-of-life and no longer receives security updates
• If the WebConsole must remain in use, deploy it within a fully isolated network segment with no access to sensitive data or internet connectivity
• Restrict Report Builder access to only essential personnel and implement strict access controls
• Conduct a thorough review of existing reports for any potentially malicious content

Patch Information

The Commvault WebConsole package is currently end-of-life and is no longer maintained. No security patches will be released for this vulnerability. Users are strongly advised to migrate away from the WebConsole to supported alternatives. For more information, refer to the Commvault Security Advisory CV_2025_06_3.

Workarounds

• Isolate the WebConsole deployment in a dedicated network segment with no connectivity to production systems or the internet
• Implement strict access controls limiting who can create and edit reports in the Report Builder
• Deploy a web application firewall (WAF) with XSS filtering rules in front of the WebConsole application
• Regularly audit report content for suspicious or malicious script elements
• Consider implementing browser-based XSS protection headers such as Content-Security-Policy where possible

# Network isolation recommendation for WebConsole deployment
# Configure firewall rules to restrict WebConsole access
# Example: Allow access only from specific management subnet

# Restrict inbound access to WebConsole port
iptables -A INPUT -p tcp --dport 443 -s 10.0.100.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP

# Block outbound internet access from WebConsole server
iptables -A OUTPUT -o eth0 -d 0.0.0.0/0 -j DROP
iptables -A OUTPUT -o eth0 -d 10.0.0.0/8 -j ACCEPT