Splunk Enterprise is a popular solution for searching, monitoring, and analyzing machine-generated data via a web-style interface. But, as with all powerful tools, vulnerabilities can sometimes emerge. One such flaw is CVE-2022-43563, which targets how the rex command in Splunk handles field names and allows attackers to skirt around SPL ("Search Processing Language") security controls. Let’s break this vulnerability down, see how it works, and look at potential real-world impacts. All content here is explained in simple, straightforward language for easy understanding.

What is CVE-2022-43563?

CVE-2022-43563 is a vulnerability in Splunk Enterprise (versions below 8.2.9 and 8.1.12) relating to how the rex search command processes field names. This flaw enables an attacker to evade built-in safeguards that restrict the use of “risky” SPL commands—operations that could, for example, leak data or modify system behavior.

- Official safeguards documentation: SPL safeguards overview
- Splunk advisory: SVD-2022-1107

The Vulnerable Mechanism

Splunk’s SPL safeguards are designed to prevent misuse of sensitive search commands for users with lower privileges. Normally, if you try to use restricted commands (like | delete, commands accessing OS-level features, or those exposing sensitive data), Splunk blocks your search.

However, if you (the attacker) cleverly craft a rex field name, you can sneak risky commands “under the radar,” bypassing these SPL security checks.

The rex command allows users to extract fields on the fly using regular expressions.

- If a malicious field name is injected in just the right way, Splunk’s parser can be tricked into letting a risky command through—even if you’re not supposed to run it.

How an Attack Works

It’s important to remember that exploitation *requires* tricking a legitimate Splunk user, usually with a phishing attack. The attacker typically crafts a search URL or link containing the malicious query. When a victim with sufficient privileges (like an admin or Power user) clicks the link, it executes in their browser.

The attacker cannot trigger the exploit at will—they need user interaction.

Attacker crafts a malicious Splunk search containing specially crafted rex field names.

2. This search is embedded in a link or sent via email/message.
3. Victim clicks the URL, opening it in a browser *where they are already logged in* to the vulnerable Splunk instance.

Sample Exploit

Let’s see a simplified, *theoretical* exploit. Suppose the risky command is something like | delete, or | sendemail, both typically blocked for most users.

index=main | rex "foo"

A *malicious* search leveraging CVE-2022-43563

index=main | rex field="|" "somefield=\\w+"

Or, an encoded variant inside a URL

https://splunk-instance/en-US/app/search/search?q=index%3Dmain%20%7Crex%20field%3D%22%7C%22%20%22somefield%3D%5Cw%2B%22

rex field="|" uses an invalid or unexpected field name that can confuse the parser.

- Splunk's safeguard logic might incorrectly parse this, allowing any command following it to slip past controls.

NOTE: Actual exploitation could involve more “subtle” query structures or complex field names designed to bypass various checks. The precise payload may depend on Splunk’s search pipeline at the time, and this PoC is for illustration only.

Possible Impacts

- Privilege escalation: Regular users could execute admin-only or sensitive commands if they can trick an admin into running a malicious search.

8.1.12 and above

If you run on earlier versions, update immediately. There are no reliable mitigations except patching.

Reference: Splunk Security Advisory SVD-2022-1107

Stay updated: Regularly patch Splunk and review advisories.

- Limit user privileges: Use the least-privilege model, so users can't run risky commands unnecessarily.
- Educate employees: Teach about phishing risks—remind everyone: "Don't click weird Splunk search links!"

Final Thoughts

While CVE-2022-43563 is not a “click-and-own” bug—it still poses a significant risk in environments with valuable data and powerful users. Phishing attacks leveraging this flaw can result in privilege escalation inside Splunk, data exposure, or worse.

Patch your Splunk now, review your user permissions, and be careful with unknown search links—even inside your internal tools. For more details, always refer to Splunk’s own documentation and advisories.

References

- Splunk Security Advisory SVD-2022-1107
- SPL Safeguards Documentation

Timeline

Published on: 11/04/2022 23:15:00 UTC
Last modified on: 11/08/2022 14:46:00 UTC