1. Introduction
The Splunk ‘/en-US/app/’ Referer Header XSS vulnerability is a cross-site scripting issue affecting Splunk installations. This allows an attacker to inject malicious code into a user’s browser, potentially stealing cookies and session information or performing actions on behalf of the user. It typically affects web servers hosting Splunk instances accessible from the internet or internal networks. Impact is likely to be high on confidentiality, medium on integrity, and low on availability.
2. Technical Explanation
The vulnerability occurs because Splunk fails to properly sanitise data received in the ‘Referer’ HTTP header. An attacker can craft a malicious URL containing JavaScript code within the Referer header. When a user clicks this link, the injected script executes in their browser within the context of the Splunk web application. The CVE identifier for this issue is CVE-2014-8380.
- Root cause: Insufficient input validation on the ‘Referer’ HTTP header.
- Exploit mechanism: An attacker sends a specially crafted URL with malicious JavaScript in the Referer header to a target user. When the user accesses Splunk, the script executes. For example, an attacker could send 3. Detection and Assessment
Confirming vulnerability requires checking the installed Splunk version and reviewing HTTP request logs for unsanitised Referer headers.
- Quick checks: Access the Splunk web interface and check the ‘About’ page to determine the installed version.
- Scanning: Nessus plugin ID 478b0c12 can detect this vulnerability as an example only.
- Logs and evidence: Examine Splunk access logs for HTTP requests containing unsanitised JavaScript code in the Referer header. The exact log path depends on your Splunk configuration.
# Example command placeholder: # No specific command available without knowing Splunk config. Check Splunk documentation for log locations.4. Solution / Remediation Steps
A solution is currently unknown at this time, so mitigation focuses on reducing exposure and monitoring for exploitation attempts.
4.1 Preparation
- Services to stop: No services need to be stopped.
- Dependencies or pre-requisites: None. Roll back plan involves restoring from the previous backup if issues occur. Change windows and approvals may be needed depending on internal policy.
4.2 Implementation
- Step 1: Monitor Splunk access logs for suspicious activity in the Referer header.
- Step 2: Implement a web application firewall (WAF) to block requests containing potentially malicious JavaScript code in the Referer header.
4.3 Config or Code Example
Before
# No configuration example available as no solution exists.After
# WAF rule example (syntax varies by vendor): Block requests with JavaScript in Referer header. # Example: If Referer contains "