In PHP versions 7.2.x below 7.2.34, 7.3.x below 7.3.23 and 7.4.x below 7.4.11, when PHP is processing incoming HTTP cookie values, the cookie names are url-decoded. This may lead to cookies with prefixes like __Host confused with cookies that decode to such prefix, thus leading to an attacker being able to forge cookie which is supposed to be secure. See also CVE-2020-8184 for more information.
Exploitability
AV:NAC:LPR:NUI:RScope
S:UImpact
C:NI:LA:N4.3/CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:NInput Validation