The path to ssl certificates has to be a full path, where as other command line options are relative to where mongod is called from.

eg my start mongod bash script:

#!/bin/bash
./bin/mongod --dbpath=./data/single --fork --logpath=./logs/single --sslPEMKeyFile=./jstests/libs/server.pem --sslCAFile=./jstests/libs/ca.pem --sslCRLFile=./jstests/libs/crl.pem --sslOnNormalPorts --sslWeakCertificateValidation --smallfiles --noprealloc --nojournal

Errors with ERROR: cannot read certificate file. When I supply the full path to the certificates it works but this is different to how dbpath and logpath work.