CVE-2020-13954: Apache CXF Reflected XSS Vulnerability

CVE-2020-13954 Overview

CVE-2020-13954 is a reflected Cross-Site Scripting (XSS) vulnerability affecting Apache CXF, a popular open-source services framework for building enterprise web services. By default, Apache CXF creates a /services page that displays available endpoint names and addresses. This webpage is vulnerable to a reflected XSS attack via the styleSheetPath parameter, which allows malicious actors to inject arbitrary JavaScript into the web page. This vulnerability is separate from the previously disclosed CVE-2019-17573.

Critical Impact

Attackers can inject malicious JavaScript code through the styleSheetPath parameter, potentially enabling session hijacking, credential theft, or delivery of malicious payloads to users visiting affected Apache CXF services pages.

Affected Products

• Apache CXF versions prior to 3.4.1
• Apache CXF versions prior to 3.3.8
• NetApp Snap Creator Framework
• NetApp VASA Provider for Clustered Data ONTAP
• Oracle Business Intelligence (versions 5.5.0.0.0, 5.9.0.0.0, 12.2.1.3.0, 12.2.1.4.0)
• Oracle Retail Order Broker Cloud Service 15.0
• Oracle Communications Messaging Server (versions 8.0.2, 8.1)

Discovery Timeline

• November 12, 2020 - CVE-2020-13954 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2020-13954

Vulnerability Analysis

This vulnerability (CWE-79) exists in the default /services endpoint page that Apache CXF automatically generates. The page is designed to provide a convenient listing of available web service endpoints and their addresses. However, the styleSheetPath parameter is not properly sanitized before being reflected back in the HTML response.

The reflected XSS vulnerability allows an attacker to craft a malicious URL containing JavaScript code in the styleSheetPath parameter. When a victim clicks on this crafted link, the malicious script executes in the context of the victim's browser session. This can lead to session token theft, unauthorized actions performed on behalf of the victim, or redirection to phishing sites.

The vulnerability requires user interaction, as the victim must click on a malicious link. However, social engineering techniques can effectively trick users into clicking these links, especially when they appear to come from trusted sources.

Root Cause

The root cause is insufficient input validation and output encoding in the Apache CXF services listing page. The styleSheetPath parameter value is reflected in the HTML response without proper sanitization, allowing attackers to break out of the expected context and inject arbitrary JavaScript. The framework fails to apply appropriate HTML entity encoding or Content Security Policy headers that would prevent script execution.

Attack Vector

The attack vector is network-based and requires user interaction. An attacker constructs a malicious URL targeting an Apache CXF deployment's /services endpoint, embedding JavaScript code within the styleSheetPath parameter. The attack flow proceeds as follows:

1. Attacker identifies a target running a vulnerable Apache CXF version
2. Attacker crafts a URL with malicious JavaScript in the styleSheetPath parameter
3. Attacker delivers the malicious URL to potential victims via email, social media, or other channels
4. Victim clicks the link, causing their browser to request the page from the legitimate server
5. The server reflects the malicious script in its response without sanitization
6. The victim's browser executes the attacker's JavaScript in the context of the trusted domain

The vulnerability is particularly concerning for internal enterprise applications where users may have elevated trust in links pointing to known service endpoints.

Detection Methods for CVE-2020-13954

Indicators of Compromise

• Suspicious URL requests to /services endpoints containing styleSheetPath parameters with encoded JavaScript or HTML tags
• Web server logs showing requests with unusual characters such as <script>, javascript:, or onerror= in query parameters
• User reports of unexpected browser behavior or pop-ups when accessing CXF services pages
• Detection of outbound connections to unknown domains after users access internal service endpoints

Detection Strategies

• Implement web application firewall (WAF) rules to detect and block requests containing XSS payloads in the styleSheetPath parameter
• Configure intrusion detection systems (IDS) to alert on patterns matching reflected XSS attack signatures targeting /services paths
• Enable verbose logging on Apache CXF endpoints and monitor for requests containing suspicious JavaScript or HTML entities
• Utilize security information and event management (SIEM) correlation rules to identify patterns of XSS exploitation attempts

Monitoring Recommendations

• Monitor web server access logs for requests to /services endpoints with unusual styleSheetPath parameter values
• Set up alerts for HTTP responses from CXF endpoints that contain unescaped script tags or JavaScript event handlers
• Track client-side JavaScript errors that may indicate XSS payload execution attempts
• Regularly audit browser security headers (Content-Security-Policy, X-XSS-Protection) on CXF deployments

How to Mitigate CVE-2020-13954

Immediate Actions Required

• Upgrade Apache CXF to version 3.4.1 or later for the 3.4.x branch
• Upgrade Apache CXF to version 3.3.8 or later for the 3.3.x branch
• If immediate patching is not possible, disable the services listing page by configuring CXF to not expose the /services endpoint
• Implement Content Security Policy (CSP) headers to mitigate the impact of XSS attacks

Patch Information

Apache has released patched versions that address this vulnerability. Organizations should upgrade to Apache CXF version 3.4.1 or later for the 3.4.x release line, or version 3.3.8 or later for the 3.3.x release line. The fix properly sanitizes the styleSheetPath parameter to prevent JavaScript injection.

For detailed information, refer to the Apache CXF CVE-2020-13954 Advisory.

Oracle customers using affected products should apply patches from the Oracle January 2021 Security Alert, Oracle April 2021 Security Alert, or Oracle October 2021 Security Alert as applicable to their deployments.

NetApp customers should consult the NetApp Security Advisory ntap-20210513-0010 for guidance on affected products.

Workarounds

• Disable the default services listing page by setting the hide-service-list-page configuration option to true in CXF configuration
• Implement a reverse proxy or WAF rule to block requests to /services endpoints containing the styleSheetPath parameter
• Deploy network-level access controls to restrict access to CXF services endpoints to authorized users and systems only
• Add Content-Security-Policy headers at the web server or load balancer level to prevent inline script execution

# Apache CXF configuration to disable services page
# Add to cxf.xml or Spring configuration
# Set the hide-service-list-page property to true
# <cxf:bus>
#   <cxf:properties>
#     <entry key="hide-service-list-page" value="true"/>
#   </cxf:properties>
# </cxf:bus>

# Alternative: Configure web server to block vulnerable parameter
# Apache HTTPD mod_rewrite example:
RewriteEngine On
RewriteCond %{QUERY_STRING} styleSheetPath= [NC]
RewriteRule ^/services - [F,L]