As per samba upstream advisory:

Some database modules make a shallow copy of an LDAP add/delete message so they can make modifications to its elements without affecting the original message. Each element in a message points to an array of values, and these arrays are shared between the original message and the copy.

The issue arises when a database module adds new values to an existing array. A call to realloc() increases the array's size to accommodate new elements, but at the same time, frees the old array. This leaves the original message element with a dangling pointer to a now-freed array. When the database audit logging module subsequently logs the details of the original message, it will access this freed data, generally resulting in corrupted log output or a crash.

The code paths susceptible to this issue are reachable when certain specific attributes, such as userAccountControl, are added or modified. These attributes are not editable by default without having a privilege assigned, such as Write Property.