There is a possibility for Regular expression Denial of Service (ReDoS) by in the cgi gem. This vulnerability has been assigned the CVE identifier CVE-2025-27220. We recommend upgrading the cgi gem.
There is a possibility for DoS by in the cgi gem. This vulnerability has been assigned the CVE identifier CVE-2025-27219. We recommend upgrading the cgi gem.
Ruby gem cgi.rb prior to versions 0.3.5, 0.2.2 and 0.1.0.2 allow HTTP header injection. If a CGI application using the CGI library inserts untrusted input into the HTTP response header, an attacker can exploit it to insert a newline character to split a header, and inject malicious content to deceive clients. This issue has been patched in versions 0.3.5, 0.2.2 and 0.1.0.2.
CGI.escape_html in Ruby has an integer overflow and resultant buffer overflow via a long string on platforms (such as Windows) where size_t and long have different numbers of bytes.
CGI::Cookie.parse in Ruby mishandles security prefixes in cookie names. This also affects the CGI gem for Ruby.
A security vulnerability that causes buffer overflow when you pass a very large string ( MB) to CGI.escape_html on a platform where long type takes 4 bytes, typically, Windows. Please update the cgi gem to,1,1 or later. You can use gem update cgi to update it. If you are using bundler, please add gem "cgi", " " to your Gemfile. Alternatively, please update Ruby to This issue has been introduced …