{"id":"CVE-2021-33621","aliases":["BIT-ruby-2021-33621","BIT-ruby-min-2021-33621","GHSA-vc47-6rqg-c7f5"],"url":"https://o3.security/vulnerability/CVE-2021-33621","summary":"HTTP response splitting in CGI","details":"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.","published":"2022-11-18T23:15:18.987Z","modified":"2026-09-16T03:45:09.181476802Z","cvss":{"score":8.8,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"},"epss":null,"cisaKev":null,"exploitsKnown":1,"affectedPackages":[{"ecosystem":"RubyGems","name":"cgi","fixedVersion":"0.3.5"},{"ecosystem":"RubyGems","name":"cgi","fixedVersion":"0.2.2"},{"ecosystem":"RubyGems","name":"cgi","fixedVersion":"0.1.0.2"}],"fix":null,"references":[{"type":"WEB","url":"https://lists.debian.org/debian-lts-announce/2023/06/msg00012.html"},{"type":"WEB","url":"https://lists.debian.org/debian-lts-announce/2024/09/msg00000.html"},{"type":"WEB","url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/DQR7LWED6VAPD5ATYOBZIGJQPCUBRJBX/"},{"type":"WEB","url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/THVTYHHEOVLQFCFHWURZYO7PVUPBHRZD/"},{"type":"WEB","url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/YACE6ORF2QBXXBK2V2CM36D7TZMEJVAS/"},{"type":"ADVISORY","url":"https://security.gentoo.org/glsa/202401-27"},{"type":"ADVISORY","url":"https://security.netapp.com/advisory/ntap-20221228-0004/"},{"type":"EVIDENCE","url":"https://www.ruby-lang.org/en/news/2022/11/22/http-response-splitting-in-cgi-cve-2021-33621/"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2021-33621"},{"type":"WEB","url":"https://hackerone.com/reports/1204695"},{"type":"WEB","url":"https://github.com/rubysec/ruby-advisory-db/blob/master/gems/cgi/CVE-2021-33621.yml"},{"type":"WEB","url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/DQR7LWED6VAPD5ATYOBZIGJQPCUBRJBX"},{"type":"WEB","url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/THVTYHHEOVLQFCFHWURZYO7PVUPBHRZD"},{"type":"WEB","url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/YACE6ORF2QBXXBK2V2CM36D7TZMEJVAS"},{"type":"WEB","url":"https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/DQR7LWED6VAPD5ATYOBZIGJQPCUBRJBX"},{"type":"WEB","url":"https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/THVTYHHEOVLQFCFHWURZYO7PVUPBHRZD"},{"type":"WEB","url":"https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/YACE6ORF2QBXXBK2V2CM36D7TZMEJVAS"},{"type":"WEB","url":"https://security.netapp.com/advisory/ntap-20221228-0004"},{"type":"WEB","url":"https://www.ruby-lang.org/en/news/2022/11/22/http-response-splitting-in-cgi-cve-2021-33621"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-09-16T03:45:09.181476802Z"}}