Web::Simple versions before 0.035 for Perl allocate a buffer sized by the Content-Length header for urlencoded body parameters. Web::Dispatch::ParamParser::get_unpacked_body_from reads an application/x-www-form-urlencoded body using a single read call, with no cap and the return value ignored. Perl's read grows the buffer to the requested length before reading, so the declared Content-Length determines the allocation. An attacker can trigger this through any route whose dispatch specification has a % body-parameter match, such as sub (POST + %name=), sending a Content-Length far larger than the body actually sent. No authentication is involved.

• https://github.com/p5sagit/Web-Simple/commit/7e02c4f6204a2898938d357e6efe6dc2679af695.patch
• https://metacpan.org/release/ETHER/Web-Simple-0.035/changes