{"id":"CVE-2021-29991","details":"Firefox incorrectly accepted a newline in a HTTP/3 header, interpretting it as two separate headers. This allowed for a header splitting attack against servers using HTTP/3. This vulnerability affects Firefox \u003c 91.0.1 and Thunderbird \u003c 91.0.1.","modified":"2026-05-04T08:37:43.520832Z","published":"2021-11-03T01:15:07.060Z","withdrawn":"2026-05-04T08:37:43.520832Z","related":["SUSE-SU-2021:14821-1","SUSE-SU-2021:14826-1","SUSE-SU-2021:3191-1","SUSE-SU-2021:3331-1","SUSE-SU-2021:3451-1","SUSE-SU-2021:4150-1","SUSE-SU-2022:1577-1","SUSE-SU-2022:1582-1","openSUSE-SU-2021:1367-1","openSUSE-SU-2021:1635-1","openSUSE-SU-2021:3331-1","openSUSE-SU-2021:3451-1","openSUSE-SU-2021:4150-1","openSUSE-SU-2024:10600-1","openSUSE-SU-2024:10601-1","openSUSE-SU-2024:14572-1"],"references":[{"type":"ADVISORY","url":"https://www.mozilla.org/security/advisories/mfsa2021-37/"},{"type":"REPORT","url":"https://bugzilla.mozilla.org/show_bug.cgi?id=1724896"}],"affected":[{"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2021-29991.json","unresolved_ranges":[{"events":[{"introduced":"0"},{"fixed":"91.0.1"}]},{"events":[{"introduced":"0"},{"fixed":"91.0.1"}]}]}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N"}]}