http://thehackernews.com/2017/07/gnupg-libgcrypt-rsa-encryption.html?utm_sou...
I believe most deployments of GnuTLS now use nettle instead of libgcrypt. But if you're on an older Debian or Ubuntu, using their packaged OpenLDAP built with GnuTLS, you should check what version of GnuTLS and libgcrypt you're using.
And you should seriously consider not using their package; rebuild from source with OpenSSL or get a package from LTB or Symas.