An issue was discovered in Cyrus IMAP before 3.12.4. There is a VPATCH BYPARAM double-free. An authenticated calendar user could crash a Cyrus CalDAV worker with a PATCH containing PATCH-ACTION="BYPARAM@..." against a resource with two or more properties of the matched kind. The memory holding the selector would be freed once on each iteration over the properties.
https://www.cyrusimap.org/3.12/imap/download/release-notes/3.8/x/3.8.8.html
https://www.cyrusimap.org/3.12/imap/download/release-notes/3.12/x/3.12.4.html
https://www.cyrusimap.org/3.12/imap/download/release-notes/3.10/x/3.10.4.html