CVE-2025-40899: Assets & Nodes XSS Vulnerability

CVE-2025-40899 Overview

A Stored Cross-Site Scripting (XSS) vulnerability was discovered in the Assets and Nodes functionality due to improper validation of an input parameter. An authenticated user with custom fields privileges can define a malicious custom field containing a JavaScript payload. When the victim views the Assets or Nodes pages, the XSS executes in their browser context, allowing the attacker to perform unauthorized actions as the victim, such as modify application data, disrupt application availability, and access limited sensitive information.

Critical Impact

Authenticated attackers can inject persistent JavaScript payloads that execute in victim browsers, enabling unauthorized data modification, availability disruption, and sensitive information access.

Affected Products

• Assets and Nodes functionality with custom fields feature
• Systems with custom fields privileges enabled
• Web applications utilizing the vulnerable input parameter handling

Discovery Timeline

• April 15, 2026 - CVE CVE-2025-40899 published to NVD
• April 15, 2026 - Last updated in NVD database

Technical Details for CVE-2025-40899

Vulnerability Analysis

This Stored Cross-Site Scripting vulnerability (CWE-79) exists due to improper validation of user-supplied input in the custom fields functionality. Unlike reflected XSS attacks, this stored variant persists the malicious payload within the application's data storage, causing it to execute each time the affected Assets or Nodes pages are rendered for any user who views them.

The attack requires an authenticated user with custom fields privileges, establishing a necessary privilege level for exploitation. However, once the malicious payload is stored, it executes automatically in the browser context of any victim who navigates to the compromised pages, potentially including administrators and other high-privilege users.

The vulnerability enables attackers to perform actions on behalf of victims, including modifying application data, disrupting application availability, and accessing sensitive information within the scope of the victim's session. The persistent nature of the attack amplifies its impact, as the payload continues to execute until the malicious custom field is identified and removed.

Root Cause

The root cause stems from insufficient input validation and output encoding when processing custom field values in the Assets and Nodes functionality. The application fails to properly sanitize user-controlled input before storing it in the database and does not adequately encode the data when rendering it in the browser. This allows JavaScript code embedded within custom field definitions to be interpreted and executed by the victim's browser rather than being treated as inert text content.

Attack Vector

The attack is executed over the network by an authenticated user with custom fields privileges. The attacker creates or modifies a custom field, injecting malicious JavaScript code into the field value. This payload is then stored persistently by the application.

When any user subsequently navigates to the Assets or Nodes pages where the custom field is displayed, the stored JavaScript executes within their browser session. The attacker can leverage this to steal session tokens, perform actions as the victim user, deface the application interface, or redirect users to malicious sites. Since the victim must interact with the vulnerable page for the payload to execute, user interaction is a required component of successful exploitation.

The vulnerability mechanism involves injecting JavaScript payloads through custom field definitions. When these fields are rendered on Assets or Nodes pages without proper output encoding, the browser interprets the malicious script and executes it in the context of the authenticated user's session. Technical details and specific exploitation patterns can be found in the Nozomi Networks Security Advisory.

Detection Methods for CVE-2025-40899

Indicators of Compromise

• Unusual JavaScript code patterns within custom field values, particularly <script> tags or event handlers like onerror, onload, or onclick
• Custom fields containing encoded payloads such as HTML entities, base64 strings, or URL-encoded JavaScript
• Unexpected modifications to custom field configurations, especially by users who don't typically manage these settings
• Browser console errors or unusual network requests originating from Assets or Nodes pages

Detection Strategies

• Implement Content Security Policy (CSP) headers and monitor for policy violation reports indicating XSS attempts
• Deploy web application firewall (WAF) rules to detect and alert on common XSS payload signatures in custom field submissions
• Enable detailed audit logging for all custom field creation and modification events
• Conduct regular security scanning of stored content for JavaScript patterns and known XSS payloads

Monitoring Recommendations

• Monitor authentication logs for unusual access patterns to the custom fields management interface
• Track user session behavior for anomalous actions that may indicate session hijacking following XSS exploitation
• Set up alerting for rapid succession of data modifications that could indicate automated exploitation
• Review application access logs for unexpected requests to sensitive endpoints following page views of Assets or Nodes

How to Mitigate CVE-2025-40899

Immediate Actions Required

• Review and audit all existing custom field values for potentially malicious JavaScript content
• Restrict custom fields privileges to only essential personnel until patches are applied
• Implement additional input validation at the application layer if possible through configuration
• Enable Content Security Policy headers to reduce the impact of any successful XSS exploitation

Patch Information

Refer to the Nozomi Networks Security Advisory for official patch information and remediation guidance. Apply vendor-provided security updates as soon as they become available to address the underlying input validation deficiency.

Workarounds

• Implement strict Content Security Policy headers with script-src 'self' to prevent inline script execution
• Disable or restrict access to the custom fields functionality until patches can be applied
• Deploy a web application firewall with XSS detection rules to filter malicious payloads
• Conduct manual review of all custom field values and remove any suspicious content

# Example Content Security Policy header configuration for Apache
# Add to httpd.conf or .htaccess
Header set Content-Security-Policy "default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline'; img-src 'self' data:; frame-ancestors 'self';"

# Example for Nginx
# Add to server block in nginx.conf
add_header Content-Security-Policy "default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline'; img-src 'self' data:; frame-ancestors 'self';";