In PHP from 8.1.* before 8.1.32, from 8.2.* before 8.2.28, from 8.3.* before 8.3.19, from 8.4.* before 8.4.5, when user-supplied headers are sent, the insufficient validation of the end-of-line characters may prevent certain headers from being sent or lead to certain headers be misinterpreted.