{"cve":"CVE-2021-41084","nvd":{"published":"2021-09-21T18:15:07.427","modified":"2026-06-17T04:07:50.633","status":"Modified","description":"http4s is an open source scala interface for HTTP. In affected versions http4s is vulnerable to response-splitting or request-splitting attacks when untrusted user input is used to create any of the following fields: Header names (`Header.name`å), Header values (`Header.value`), Status reason phrases (`Status.reason`), URI paths (`Uri.Path`), URI authority registered names (`URI.RegName`) (through 0.21). This issue has been resolved in versions 0.21.30, 0.22.5, 0.23.4, and 1.0.0-M27 perform the following. As a matter of practice http4s services and client applications should sanitize any user input in the aforementioned fields before returning a request or response to the backend. The carriage return, newline, and null characters are the most threatening.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:L/A:N","score":4.7},"cwes":["CWE-74","CWE-918"],"references":["https://github.com/http4s/http4s/commit/d02007db1da4f8f3df2dbf11f1db9ac7afc3f9d8","https://github.com/http4s/http4s/security/advisories/GHSA-5vcm-3xc3-w7x3","https://httpwg.org/http-core/draft-ietf-httpbis-semantics-latest.html#fields.values","https://owasp.org/www-community/attacks/HTTP_Response_Splitting","https://github.com/http4s/http4s/commit/d02007db1da4f8f3df2dbf11f1db9ac7afc3f9d8"],"products":["typelevel:http4s"],"source":"nvd","synced_at":"2026-10-19T21:23:41.316049955+00:00"},"epss":{"cve":"CVE-2021-41084","score":0.01235,"percentile":0.69054,"date":"2026-11-01"},"kev":null,"osv":[{"id":"GHSA-5vcm-3xc3-w7x3","url":"https://osv.dev/vulnerability/GHSA-5vcm-3xc3-w7x3","summary":"Response Splitting from unsanitized headers","modified":"2026-07-08T06:27:29.641386159Z","packages":[{"ecosystem":"Maven","name":"org.http4s:http4s-client_2.12","purl":"pkg:maven/org.http4s/http4s-client_2.12","ranges":["<0.21.29"],"fixed":["0.21.29"]},{"ecosystem":"Maven","name":"org.http4s:http4s-client_2.12","purl":"pkg:maven/org.http4s/http4s-client_2.12","ranges":[">=0.22.0 <0.22.5"],"fixed":["0.22.5"]},{"ecosystem":"Maven","name":"org.http4s:http4s-client_2.12","purl":"pkg:maven/org.http4s/http4s-client_2.12","ranges":[">=0.23.0 <0.23.4"],"fixed":["0.23.4"]},{"ecosystem":"Maven","name":"org.http4s:http4s-client_2.13","purl":"pkg:maven/org.http4s/http4s-client_2.13","ranges":["<0.21.29"],"fixed":["0.21.29"]},{"ecosystem":"Maven","name":"org.http4s:http4s-client_2.13","purl":"pkg:maven/org.http4s/http4s-client_2.13","ranges":[">=0.22.0 <0.22.5"],"fixed":["0.22.5"]},{"ecosystem":"Maven","name":"org.http4s:http4s-client_2.13","purl":"pkg:maven/org.http4s/http4s-client_2.13","ranges":[">=0.23.0 <0.23.4"],"fixed":["0.23.4"]},{"ecosystem":"Maven","name":"org.http4s:http4s-client_3","purl":"pkg:maven/org.http4s/http4s-client_3","ranges":["<0.21.29"],"fixed":["0.21.29"]},{"ecosystem":"Maven","name":"org.http4s:http4s-client_3","purl":"pkg:maven/org.http4s/http4s-client_3","ranges":[">=0.22.0 <0.22.5"],"fixed":["0.22.5"]},{"ecosystem":"Maven","name":"org.http4s:http4s-client_3","purl":"pkg:maven/org.http4s/http4s-client_3","ranges":[">=0.23.0 <0.23.4"],"fixed":["0.23.4"]},{"ecosystem":"Maven","name":"org.http4s:http4s-server_2.10","purl":"pkg:maven/org.http4s/http4s-server_2.10","ranges":["<=0.21.28"],"fixed":[]},{"ecosystem":"Maven","name":"org.http4s:http4s-server_2.11","purl":"pkg:maven/org.http4s/http4s-server_2.11","ranges":["<=0.21.28"],"fixed":[]},{"ecosystem":"Maven","name":"org.http4s:http4s-server_2.12","purl":"pkg:maven/org.http4s/http4s-server_2.12","ranges":["<0.21.29"],"fixed":["0.21.29"]},{"ecosystem":"Maven","name":"org.http4s:http4s-server_2.12","purl":"pkg:maven/org.http4s/http4s-server_2.12","ranges":[">=0.22.0 <0.22.5"],"fixed":["0.22.5"]},{"ecosystem":"Maven","name":"org.http4s:http4s-server_2.12","purl":"pkg:maven/org.http4s/http4s-server_2.12","ranges":[">=0.23.0 <0.23.4"],"fixed":["0.23.4"]},{"ecosystem":"Maven","name":"org.http4s:http4s-server_2.13","purl":"pkg:maven/org.http4s/http4s-server_2.13","ranges":["<0.21.29"],"fixed":["0.21.29"]},{"ecosystem":"Maven","name":"org.http4s:http4s-server_2.13","purl":"pkg:maven/org.http4s/http4s-server_2.13","ranges":[">=0.22.0 <0.22.5"],"fixed":["0.22.5"]},{"ecosystem":"Maven","name":"org.http4s:http4s-server_2.13","purl":"pkg:maven/org.http4s/http4s-server_2.13","ranges":[">=0.23.0 <0.23.4"],"fixed":["0.23.4"]},{"ecosystem":"Maven","name":"org.http4s:http4s-server_2.13.0-M5","purl":"pkg:maven/org.http4s/http4s-server_2.13.0-M5","ranges":["<=0.21.28"],"fixed":[]},{"ecosystem":"Maven","name":"org.http4s:http4s-server_3","purl":"pkg:maven/org.http4s/http4s-server_3","ranges":[">=0.22.0 <0.22.5"],"fixed":["0.22.5"]},{"ecosystem":"Maven","name":"org.http4s:http4s-server_3","purl":"pkg:maven/org.http4s/http4s-server_3","ranges":[">=0.23.0 <0.23.4"],"fixed":["0.23.4"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}