When a UDF filesystem contains directories that do not have UDF execute permission set, it is impossible to access those directories from any user except for root.  There are no mount options that can work around this either.

There are quite a number of UDF disks out there, including commercial installation media from well known companies which do not use the execute bit for directories on UDF filesystems.

The UDF specification at http://www.ecma-international.org/publications/standards/Ecma-167.htm defines that files with the execute bit set "may execute the file", but execute permission on directories are completely undefined in the spec.  The notion of executable directories would be seen as an oddity under a straightforward reading of the spec.

The UDF filesystem driver presently treats UDF filesystems with the assumption that listing the contents of directories cannot be accessed by ordinary users if they do not have execute permission.  This is normal in unix, but it isn't  a documented UDF assumption, being absent from the UDF spec.

I believe that the UDF filesystem should have mount option(s) to override directory permissions, adding the execute bit in its absence.  Consideration should be given as to whether this should be the default behaviour.