UBUNTU-CVE-2026-120636: Medium severity ubuntu/libcgi-pm-perl vulnerability

CGI versions before 5.00 for Perl allow open redirects and script injection via URLs built from REQUESTURI in url and startform. url(-absolute=>1), url(-relative=>1) and the default startform action are built from the client-supplied REQUESTURI without validation. The result can be protocol-relative (//evil.example), absolute-form (http://evil.example/) or contain backslashes, and url(-relative=>1) can return a javascript: URL. Links and form posts built from these URLs can go to another host.