To reproduce: Run curl -F 'field=<-' 'http://example.com/', then type "abc\n" and press ^D; curl will continue waiting for input until you press ^D a second time.

The bug is caused by the use of fread() in Curl_getformdata() (code at the time of writing). In the example above, fread() will return 4 after the first call, even at EOF. To handle EOF correctly, the code should check feof() explicitly.