The general weakness of SHA has been understood for some time, although progress advances on finding collisions (Such as https://security.googleblog.com/2017/02/announcing-first-sha1-collision.html?m=1).
I think it would be wise to update OpenLDAP to a different default for userPassword. We currently have the Contrib SHA2 module, and there's a nice bcrypt(*) module on Github (I asked the author if they would be willing to contribute it, but they seem to have gone silent).
It may be time to move the SHA2 module into core, but there has been some discussion of the limitations of the current SHA2 module in the past that would likely need addressing.
What do other folks think?
* https://github.com/wclarie/openldap-bcrypt/issues/1
--Quanah
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Quanah Gibson-Mount Product Architect Symas Corporation Packaged, certified, and supported LDAP solutions powered by OpenLDAP: http://www.symas.com