Checkmk Werk 14381: Fix command injection in SMS notification script

ID: 14381 Title: Fix command injection in SMS notification script Component: Notifications Level: 1 Class: Security fix Version: 2.2.0i1 Previous to this Werk it was possible to inject arbitrary shell commands when sending SMS notifications. For this, attackers would have needed to place a crafted string in a user's Pager Address, which was not properly escaped by the SMS script. In most setups, this issue will not be exploitable: Changing a user's Pager Address requires the User Management permission. Users with that permission are effectively Administrators and can thus already legitimately execute code in the Site context. Note however, that in some setups the attribute can also be configured by external interfaces, for example via LDAP User Synchronization. <b>Affected Versions</b>: All currently supported versions are affected: 1.6, 2.0, and 2.1. <b>Mitigations</b>: As an immediate mitigation all notifications via the method "SMS (using smstools)" can be disabled. Note that users' personal notification rules are affected as well. <b>Indicators of Compromise</b>: If you suspect this issue might have been exploited in your installation, validate users' Pager Address fields. Check the Audit Log for changes to this field. <b>Vulnerability Management</b>: We have rated the issue with a CVSS Score of 8.0 (High) with the following CVSS vector: <tt>CVSS:3.1/AV:A/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H</tt>. A CVE has been requested. <b>Changes</b>: This Werk replaces a hazardous call to <tt>os.system</tt> by a safer alternative and adds additional validation to the Pager Address before attempting to send SMS to it. Valid Pager Addresses may now include letters, numbers, space characters, any of the characters <tt>. / - ()</tt>, as well as a <tt>+</tt> character at the beginning.