{"id":"CVE-2021-22903","url":"https://www.cyber-defence.io/tools/cve/CVE-2021-22903","generatedAt":"2026-10-28T01:52:14.112Z","title":"The actionpack ruby gem before 6.1.3.2 suffers from a possible open redirect vulnerability.","description":"The actionpack ruby gem before 6.1.3.2 suffers from a possible open redirect vulnerability. Specially crafted Host headers in combination with certain \"allowed host\" formats can cause the Host Authorization middleware in Action Pack to redirect users to a malicious website. This is similar to CVE-2021-22881. Strings in config.hosts that do not have a leading dot are converted to regular expressions without proper escaping. This causes, for example, `config.hosts << \"sub.example.com\"` to permit a request with a Host header value of `sub-example.com`.","published":"2021-06-11T16:15:11.000Z","lastModified":"2026-06-17T03:38:00.000Z","status":"Modified","sourceIdentifier":"support@hackerone.com","cvss":{"version":"3.1","score":6.1,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N"},"cwe":["CWE-601"],"affected":["rubyonrails/rails"],"epss":{"score":0.0123,"percentile":0.68729,"date":"2026-10-26","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"low","text":"Lower severity and a low EPSS score (1.23%). Track it; it rarely justifies an emergency change on its own."},"changes":[],"references":[{"url":"https://discuss.rubyonrails.org/t/cve-2021-22903-possible-open-redirect-vulnerability-in-action-pack/77867","tags":["Mitigation","Patch","Vendor Advisory"],"source":"support@hackerone.com"},{"url":"https://hackerone.com/reports/1148025","tags":["Permissions Required","Third Party Advisory"],"source":"support@hackerone.com"},{"url":"https://discuss.rubyonrails.org/t/cve-2021-22903-possible-open-redirect-vulnerability-in-action-pack/77867","tags":["Mitigation","Patch","Vendor Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://hackerone.com/reports/1148025","tags":["Permissions Required","Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2021-22903","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}