CVE-2021-29991
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 < 91.0.1 and Thunderbird < 91.0.1. Date published : 2021-11-02 https://bugzilla.mozilla.org/show_bug.cgi?id=1724896