Ruby: CVE-2021-33621: HTTP response splitting in CGI

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A new Ruby blog post/announcement has been posted!

We have released the cgi gem version 0.3.5, 0.2.2, and 0.1.0.2 that has a security fix for a HTTP response splitting vulnerability. This vulnerability has been assigned the CVE identifier CVE-2021-33621.

Details

If an application that generates HTTP responses using the cgi gem with untrusted user input, an attacker can exploit it to inject a malicious HTTP response header and/or body.

Also, the contents for a CGI::Cookie object were not checked properly. If an application creates a CGI::Cookie object based on user input, an attacker may exploit it to inject invalid attributes in Set-Cookie header. We think such applications are unlikely, but we have included a change to check arguments for https://www.ruby-lang.org/en/news/2022/11/22/http-response-splitting-in-cgi-cve-2021-33621/

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