CVE-2025-20297: Splunk Enterprise XSS Vulnerability

CVE-2025-20297 Overview

CVE-2025-20297 is a Cross-Site Scripting (XSS) vulnerability affecting Splunk Enterprise and Splunk Cloud Platform. The flaw exists in the pdfgen/render REST endpoint, where a low-privileged user without "admin" or "power" Splunk roles can craft a malicious payload that results in the execution of unauthorized JavaScript code in another user's browser. This vulnerability enables attackers to potentially hijack user sessions, steal sensitive data, or perform actions on behalf of authenticated users.

Critical Impact

A low-privileged attacker can exploit this XSS vulnerability to execute arbitrary JavaScript in the context of other users' browser sessions, potentially leading to credential theft, session hijacking, or further compromise of the Splunk environment.

Affected Products

• Splunk Enterprise versions below 9.4.2, 9.3.4, and 9.2.6
• Splunk Cloud Platform versions below 9.3.2411.102, 9.3.2408.111, and 9.2.2406.118

Discovery Timeline

• 2025-06-02 - CVE-2025-20297 published to NVD
• 2025-08-01 - Last updated in NVD database

Technical Details for CVE-2025-20297

Vulnerability Analysis

This vulnerability is classified as CWE-79 (Improper Neutralization of Input During Web Page Generation), commonly known as Cross-Site Scripting (XSS). The attack requires network access and user interaction, where a victim must interact with a maliciously crafted link or content. The scope is changed, meaning the vulnerable component impacts resources beyond its security scope—in this case, the victim's browser session.

The vulnerability allows attackers with low-level privileges to bypass the expected authorization model. Even without administrative access to Splunk, an attacker can leverage the pdfgen/render endpoint to inject malicious scripts that execute in the security context of other users who may have elevated privileges.

Root Cause

The root cause of CVE-2025-20297 lies in insufficient input validation and output encoding within the pdfgen/render REST endpoint. User-supplied data is not properly sanitized before being rendered in the response, allowing attackers to inject JavaScript payloads that execute when the content is processed by a victim's browser.

The PDF generation functionality fails to adequately neutralize special characters and script content, creating an injection point that bypasses normal security controls.

Attack Vector

The attack is conducted over the network and requires user interaction. An attacker with low-level Splunk privileges crafts a malicious request to the pdfgen/render endpoint containing JavaScript payloads. When another user—potentially with higher privileges—accesses the rendered content, the malicious JavaScript executes in their browser context.

The vulnerability exploits insufficient input sanitization in the PDF rendering pipeline. An attacker constructs a request containing embedded JavaScript that bypasses input filtering. When processed by the pdfgen/render endpoint and rendered in a victim's browser, the unsanitized script executes with the victim's session context. For detailed technical information, refer to the Splunk Security Advisory SVD-2025-0601.

Detection Methods for CVE-2025-20297

Indicators of Compromise

• Unusual or malformed requests to the pdfgen/render REST endpoint containing script tags or JavaScript event handlers
• Splunk internal logs showing access to the pdfgen/render endpoint from low-privileged user accounts
• Browser-side alerts or anomalous behavior following interaction with Splunk-generated PDF content

Detection Strategies

• Monitor Splunk access logs for suspicious patterns in requests to /services/pdfgen/render containing encoded script payloads or HTML entities
• Implement web application firewall (WAF) rules to detect and block XSS patterns in requests to Splunk endpoints
• Review audit logs for low-privileged users making repeated requests to the PDF generation functionality
• Deploy endpoint detection to identify browser-based script injection attempts originating from Splunk sessions

Monitoring Recommendations

• Enable detailed logging for Splunk REST API endpoints, particularly pdfgen/render
• Configure SIEM alerts for requests containing common XSS payload patterns such as <script>, javascript:, or event handlers like onerror, onload
• Monitor for session anomalies where low-privileged accounts trigger actions typically associated with administrative users
• Implement Content Security Policy (CSP) headers to mitigate the impact of successful XSS exploitation

How to Mitigate CVE-2025-20297

Immediate Actions Required

• Upgrade Splunk Enterprise to version 9.4.2, 9.3.4, or 9.2.6 or later depending on your release branch
• Upgrade Splunk Cloud Platform to version 9.3.2411.102, 9.3.2408.111, or 9.2.2406.118 or later
• Review user accounts with access to the pdfgen/render endpoint and apply principle of least privilege
• Audit recent access logs for exploitation attempts prior to patching

Patch Information

Splunk has released security updates addressing this vulnerability. Organizations should apply the appropriate patch based on their deployment version. Detailed patch information and upgrade instructions are available in the Splunk Security Advisory SVD-2025-0601.

Workarounds

• Restrict access to the pdfgen/render endpoint to only trusted users with legitimate business needs
• Implement network-level controls to limit access to Splunk REST APIs from untrusted network segments
• Deploy a Web Application Firewall (WAF) with XSS detection rules in front of Splunk web interfaces
• Consider temporarily disabling PDF generation functionality if not critical to operations until patches can be applied

# Example: Restrict access to pdfgen endpoint via Splunk authorize.conf
# Add to $SPLUNK_HOME/etc/system/local/authorize.conf

[capability::run_pdfgen]
grantableRoles = admin;power