UBUNTU-CVE-2026-120632: Medium severity ubuntu/libcgi-pm-perl vulnerability

CGI versions before 5.00 for Perl allow CPU exhaustion via a backtracking regex on the XForms multipart/related Content-Type. When a POST Content-Type contains multipart/related, the boundary and start parameters are extracted with an unanchored pattern that puts .+ on either side of the boundary capture, which backtracks in cubic time on a header that does not match. No request body is needed.