A segfault is logged in the server log if the voms server is passed an empty (but well formed) XML document (such as <voms></voms>)
The output in server system log looks like:
voms[6681]: segfault at 0 ip 000000307f49d238 sp 00007fff4a971710 error 4 in libstdc++.so.6.0.13[307f400000+e8000]

The server does not crash since the segfault is in the forked process serving the request.

The problem can be reproduced using the openssl s_client command.

$ cat voms
<voms>
</voms>
lapventuri:~ valerioventuri$ cat voms | openssl s_client -connect vgrid02:15001 -ign_eof -cert usercert.pem -key userkey.pem