{"id":"CVE-2021-4138","aliases":["EUVD-2021-34008","GHSA-2h28-m3qw-8www"],"status":"published","title":"Improved Host header checks to reject requests not sent to a well-known local hostname or IP, or...","description":"Improved Host header checks to reject requests not sent to a well-known local hostname or IP, or the server-specified hostname.","severity":{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N","level":"medium","assessor":"primary","from":"nvd"},"epss":{"day":"2026-11-11","score":0.00847,"percentile":0.58518,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":false},"published":"2022-05-02T22:08:07Z","modified":"2026-10-20T10:54:58Z","products":[{"vendor":"mozilla","product":"geckodriver"}],"references":[{"url":"https://github.com/mozilla/geckodriver/releases/tag/v0.30.0","tags":["x_refsource_MISC","x_transferred","Release Notes","Third Party Advisory","advisory"]},{"url":"https://bugzilla.mozilla.org/show_bug.cgi?id=1652612","tags":["x_refsource_MISC","x_transferred","Issue Tracking","Permissions Required","Third Party Advisory","report"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2021-4138"},{"url":"https://github.com/advisories/GHSA-2h28-m3qw-8www"}],"sources":{"cve":[{"id":"CVE-2021-4138","description":"Improved Host header checks to reject requests not sent to a well-known local hostname or IP, or the server-specified hostname.","status":"published","published":"2022-05-02T22:08:07Z","modified":"2024-08-03T17:16:04.258Z","updated_at":"2026-11-02T14:33:07.697752Z"}],"euvd":[{"id":"EUVD-2021-34008","description":"Improved Host header checks to reject requests not sent to a well-known local hostname or IP, or the server-specified hostname.","status":"published","published":"2022-05-02T22:08:07Z","modified":"2024-08-03T17:16:04Z","updated_at":"2026-11-03T03:25:10.888157Z"}],"ghsa":[{"id":"GHSA-2h28-m3qw-8www","title":"Improved Host header checks to reject requests not sent to a well-known local hostname or IP, or...","description":"Improved Host header checks to reject requests not sent to a well-known local hostname or IP, or the server-specified hostname.","status":"published","published":"2022-05-04T00:00:27Z","modified":"2023-02-01T05:01:34Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N","level":"medium"}],"updated_at":"2026-11-02T14:49:44.873647Z"}],"nvd":[{"id":"CVE-2021-4138","description":"Improved Host header checks to reject requests not sent to a well-known local hostname or IP, or the server-specified hostname.","status":"published","published":"2022-05-02T23:15:08.057Z","modified":"2026-06-17T04:19:06.103Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N","level":"medium","assessor":"primary"},{"version":"2.0","score":5,"vector":"AV:N/AC:L/Au:N/C:N/I:P/A:N","level":"medium","assessor":"primary"}],"updated_at":"2026-11-02T14:07:06.029737Z"}],"osv":[{"id":"CVE-2021-4138","description":"Improved Host header checks to reject requests not sent to a well-known local hostname or IP, or the server-specified hostname.","status":"published","published":"2022-05-02T23:15:08.057Z","modified":"2026-10-20T10:54:58.388122636Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N","level":"medium"}],"updated_at":"2026-11-02T15:44:21.557945Z"}]}}