CGI versions from 4.71 before 5.00 for Perl allow denial of service via a plain string dereferenced as a symbolic reference in uploadInfo. uploadInfo dereferences its argument and calls its filename method without checking that it is an upload filehandle. A plain string naming a defined global variable, such as the parameter value from ?upload=0, is treated as a symbolic reference, and the method call on it dies.
https://metacpan.org/release/LEEJO/CGI-5.00/changes
https://metacpan.org/release/LEEJO/CGI-4.72/source/lib/CGI.pm
https://github.com/leejo/CGI.pm/commit/a14a7decfdc18f2daf436d30df9b543e3f0f8da3.patch