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[R2] Check_MK Multisite Web UI Stored and Reflected XSS

Medium

Synopsis

An internal server error can be triggered on the Check_MK Multisite web interface by providing an unexpected format to the output_format parameter. The internal server error page will then display output from the Apache error log. A remote unauthenticated attacker can introduce both reflected and stored HTML/Javascript to the error log using the output_format parameter or by the username in a failed HTTP basic authentication login attempt.

For example, visiting the following URL on an affected target will create a popup box. The target will also persist the code in the Apache error log so that the next user to view the internal server error page will also see the popup.

http://[target]/[sitename]/check_mk/login.py?output_format=<script>alert(%27Tenable%27)</script>

Solution

The vendor has released Check_MK versions 1.2.8p25 and 1.4.0p9 to address this issue.

Disclosure Timeline

2017-06-28 - Issue discovered
2017-07-04 - Disclosed to security at check-mk.org
2017-07-06 - Team at Check_MK confirm vulnerability, introduce fix for next release.
2017-07-24 - Fixed release 1.4.0p9 added to check-mk.org
2017-07-25 - Fixed release 1.2.8p25 added to check-mk.org
2017-08-16 - CVE requested / received

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