Core:
    Fixed bug #81076 (incorrect debug info on Closures with implicit binds).
    Fixed bug #81068 (Double free in realpath_cache_clean()).
    Fixed bug #76359 (open_basedir bypass through adding "..").
    Fixed bug #81090 (Typed property performance degradation with .= operator).
    Fixed bug #81070 (Integer underflow in memory limit comparison).
    Fixed bug #81122 (SSRF bypass in FILTER_VALIDATE_URL). (CVE-2021-21705)
Bzip2:
    Fixed bug #81092 (fflush before stream_filter_remove corrupts stream).
Fileinfo:
    Fixed bug #80197 (implicit declaration of function 'magic_stream' is invalid).
GMP:
    Fixed bug #81119 (GMP operators throw errors with wrong parameter names).
OCI8:
    Fixed bug #81088 (error in regression test for oci_fetch_object() and oci_fetch_array()).
Opcache:
    Fixed bug #81051 (Broken property type handling after incrementing reference).
    Fixed bug #80968 (JIT segfault with return from required file).
OpenSSL:
    Fixed bug #76694 (native Windows cert verification uses CN as sever name).
MySQLnd:
    Fixed bug #80761 (PDO uses too much memory).
PDO_Firebird:
    Fixed bug #76448 (Stack buffer overflow in firebird_info_cb). (CVE-2021-21704)
    Fixed bug #76449 (SIGSEGV in firebird_handle_doer). (CVE-2021-21704)
    Fixed bug #76450 (SIGSEGV in firebird_stmt_execute). (CVE-2021-21704)
    Fixed bug #76452 (Crash while parsing blob data in firebird_fetch_blob). (CVE-2021-21704)
readline:
    Fixed bug #72998 (invalid read in readline completion).
Standard:
    Fixed bug #81048 (phpinfo(INFO_VARIABLES) "Array to string conversion").
    Fixed bug #77627 (method_exists on Closure::__invoke inconsistency).
Windows:
    Fixed bug #81120 (PGO data for main PHP DLL are not used).