Confirmed the crash on zesty with openvpn-auth-ldap 2.0.3-6.1:

ubuntu@zesty-openvpn-server-1602813:/etc/openvpn$ sudo openvpn --config server.conf
Mon Jul 24 15:05:38 2017 OpenVPN 2.4.0 x86_64-pc-linux-gnu [SSL (OpenSSL)] [LZO] [LZ4] [EPOLL] [PKCS11] [MH/PKTINFO] [AEAD] built on Jun 22 2017
Mon Jul 24 15:05:38 2017 library versions: OpenSSL 1.0.2g  1 Mar 2016, LZO 2.08
Mon Jul 24 15:05:38 2017 TUN/TAP device tun0 opened
Mon Jul 24 15:05:38 2017 Note: Cannot set tx queue length on tun0: Operation not permitted (errno=1)
Mon Jul 24 15:05:38 2017 do_ifconfig, tt->did_ifconfig_ipv6_setup=0
Mon Jul 24 15:05:38 2017 /sbin/ip link set dev tun0 up mtu 1500
Mon Jul 24 15:05:38 2017 /sbin/ip addr add dev tun0 local 10.8.0.1 peer 10.8.0.2
Mon Jul 24 15:05:38 2017 Could not determine IPv4/IPv6 protocol. Using AF_INET
Mon Jul 24 15:05:38 2017 UDPv4 link local (bound): [AF_INET][undef]:1194
Mon Jul 24 15:05:38 2017 UDPv4 link remote: [AF_UNSPEC]
Mon Jul 24 15:05:38 2017 Initialization Sequence Completed
Mon Jul 24 15:10:38 2017 10.0.100.42:1194 peer info: IV_VER=2.3.10
Mon Jul 24 15:10:38 2017 10.0.100.42:1194 peer info: IV_PLAT=linux
Mon Jul 24 15:10:38 2017 10.0.100.42:1194 peer info: IV_PROTO=2
openvpn: sasl.c:273: ldap_parse_sasl_bind_result: Assertion `res != NULL' failed.
Aborted (core dumped)


Crash avoided with openvpn-auth-ldap-2.0.3-6.1ubuntu0.17.04.1 from proposed. I get a timeout as expected:
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The following packages will be upgraded:
  openvpn-auth-ldap
1 upgraded, 0 newly installed, 0 to remove and 11 not upgraded.
Need to get 36.4 kB of archives.
After this operation, 30.7 kB disk space will be freed.
Get:1 http://br.archive.ubuntu.com/ubuntu zesty-proposed/universe amd64 openvpn-auth-ldap amd64 2.0.3-6.1ubuntu0.17.04.1 [36.4 kB]
Fetched 36.4 kB in 0s (469 kB/s)       
(Reading database ... 26983 files and directories currently installed.)
Preparing to unpack .../openvpn-auth-ldap_2.0.3-6.1ubuntu0.17.04.1_amd64.deb ...
Unpacking openvpn-auth-ldap (2.0.3-6.1ubuntu0.17.04.1) over (2.0.3-6.1) ...
Setting up openvpn-auth-ldap (2.0.3-6.1ubuntu0.17.04.1) ...

ubuntu@zesty-openvpn-server-1602813:/etc/openvpn$ sudo openvpn --config server.conf
Mon Jul 24 15:13:08 2017 OpenVPN 2.4.0 x86_64-pc-linux-gnu [SSL (OpenSSL)] [LZO] [LZ4] [EPOLL] [PKCS11] [MH/PKTINFO] [AEAD] built on Jun 22 2017
Mon Jul 24 15:13:08 2017 library versions: OpenSSL 1.0.2g  1 Mar 2016, LZO 2.08
Mon Jul 24 15:13:08 2017 TUN/TAP device tun0 opened
Mon Jul 24 15:13:08 2017 Note: Cannot set tx queue length on tun0: Operation not permitted (errno=1)
Mon Jul 24 15:13:08 2017 do_ifconfig, tt->did_ifconfig_ipv6_setup=0
Mon Jul 24 15:13:08 2017 /sbin/ip link set dev tun0 up mtu 1500
Mon Jul 24 15:13:08 2017 /sbin/ip addr add dev tun0 local 10.8.0.1 peer 10.8.0.2
Mon Jul 24 15:13:08 2017 Could not determine IPv4/IPv6 protocol. Using AF_INET
Mon Jul 24 15:13:08 2017 UDPv4 link local (bound): [AF_INET][undef]:1194
Mon Jul 24 15:13:08 2017 UDPv4 link remote: [AF_UNSPEC]
Mon Jul 24 15:13:08 2017 Initialization Sequence Completed
Mon Jul 24 15:13:14 2017 10.0.100.42:1194 peer info: IV_VER=2.3.10
Mon Jul 24 15:13:14 2017 10.0.100.42:1194 peer info: IV_PLAT=linux
Mon Jul 24 15:13:14 2017 10.0.100.42:1194 peer info: IV_PROTO=2
LDAP bind failed: Timed out
Unable to bind as uid=john,ou=People,dc=lxd
LDAP connect failed.
Mon Jul 24 15:13:15 2017 10.0.100.42:1194 PLUGIN_CALL: plugin function PLUGIN_AUTH_USER_PASS_VERIFY failed with status 1: /usr/lib/openvpn/openvpn-auth-ldap.so
Mon Jul 24 15:13:15 2017 10.0.100.42:1194 TLS Auth Error: Auth Username/Password verification failed for peer
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