CVE-2024-36991: Splunk Enterprise Path Traversal Flaw

CVE-2024-36991 Overview

CVE-2024-36991 is a path traversal vulnerability affecting Splunk Enterprise on Windows systems. The vulnerability exists in the /modules/messaging/ endpoint, allowing attackers to traverse the file system and potentially access sensitive files outside the intended directory structure. This vulnerability exclusively impacts Splunk Enterprise deployments running on Windows platforms.

Critical Impact

Unauthenticated attackers can exploit this path traversal vulnerability to read arbitrary files on Windows-based Splunk Enterprise servers, potentially exposing configuration files, credentials, and other sensitive data.

Affected Products

• Splunk Enterprise on Windows versions below 9.2.2
• Splunk Enterprise on Windows versions below 9.1.5
• Splunk Enterprise on Windows versions below 9.0.10

Discovery Timeline

• 2024-07-01 - CVE-2024-36991 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2024-36991

Vulnerability Analysis

This path traversal vulnerability (CWE-22, CWE-35) allows attackers to manipulate file path inputs to escape the intended directory structure. The vulnerability is particularly dangerous because it can be exploited remotely without authentication. The /modules/messaging/ endpoint in Splunk Enterprise on Windows fails to properly sanitize user-supplied path parameters, enabling directory traversal sequences to access files outside the web application's root directory.

The Windows-specific nature of this vulnerability likely stems from differences in path handling between operating systems. Windows uses backslashes as path separators and may handle certain traversal sequences differently than Unix-based systems, which explains why only Windows deployments are affected.

Root Cause

The root cause is improper input validation in the /modules/messaging/ endpoint. The application fails to adequately sanitize or validate user-supplied path parameters before using them in file system operations. This allows attackers to inject directory traversal sequences (such as ../ or ..\) that escape the intended directory boundaries and access arbitrary files on the system.

Attack Vector

The attack is network-based and requires no authentication or user interaction. An attacker can craft malicious HTTP requests to the /modules/messaging/ endpoint containing path traversal sequences. When processed by the vulnerable Splunk Enterprise instance on Windows, these requests can read files from arbitrary locations on the file system.

The vulnerability manifests when specially crafted path components are sent to the messaging endpoint. Due to insufficient path canonicalization, the server processes these requests and returns file contents from outside the intended directory. See the Splunk Security Advisory SVD-2024-0711 for additional technical details.

Detection Methods for CVE-2024-36991

Indicators of Compromise

• HTTP requests to /modules/messaging/ containing directory traversal patterns such as ../, ..\, or URL-encoded variants
• Unusual file access attempts in Splunk internal logs showing paths outside normal application directories
• Access log entries with suspicious path patterns targeting the messaging module endpoint
• Unexpected outbound data transfers from Splunk Enterprise servers

Detection Strategies

• Monitor web access logs for requests to /modules/messaging/ containing traversal sequences like ../, ..%2f, or ..%5c
• Implement Web Application Firewall (WAF) rules to detect and block path traversal attempts
• Use the Splunk Research detection provided by Splunk to identify exploitation attempts
• Review Splunk internal logs for anomalous file access patterns

Monitoring Recommendations

• Enable verbose logging on Splunk Enterprise instances to capture detailed request information
• Configure alerting for any access attempts to the /modules/messaging/ endpoint with unusual characters
• Monitor for unauthorized file reads, particularly targeting sensitive configuration files like server.conf or passwd
• Implement network-level monitoring for suspicious traffic patterns targeting Splunk web interfaces

How to Mitigate CVE-2024-36991

Immediate Actions Required

• Upgrade Splunk Enterprise on Windows to version 9.2.2, 9.1.5, or 9.0.10 (or later) depending on your version branch
• Restrict network access to Splunk Enterprise web interfaces to trusted IP addresses only
• Implement WAF rules to block path traversal attempts at the network perimeter
• Review access logs for evidence of prior exploitation attempts

Patch Information

Splunk has released security patches addressing this vulnerability. Organizations should upgrade to the following fixed versions:

• Version 9.2.2 or later for the 9.2.x branch
• Version 9.1.5 or later for the 9.1.x branch
• Version 9.0.10 or later for the 9.0.x branch

Refer to the Splunk Security Advisory SVD-2024-0711 for official patch download links and installation instructions.

Workarounds

• Implement network-level access controls to restrict access to Splunk Enterprise web interfaces from untrusted networks
• Deploy a reverse proxy or WAF in front of Splunk Enterprise to filter malicious requests containing path traversal patterns
• Consider temporarily disabling or restricting access to the /modules/messaging/ endpoint if not required for operations
• Monitor for exploitation attempts while planning the upgrade to a patched version

# Example: Restrict access to Splunk web interface using Windows Firewall
# Allow only trusted management network (adjust IP range as needed)
netsh advfirewall firewall add rule name="Restrict Splunk Web" dir=in action=block protocol=tcp localport=8000
netsh advfirewall firewall add rule name="Allow Splunk Web Trusted" dir=in action=allow protocol=tcp localport=8000 remoteip=10.0.0.0/8