Description:
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Calling isSet with too many parameters causes a stack overflow.
Executing the test script results in a stack overflow.
The produced ASAN output can be found here: https://github.com/pnoltof/php_bug/blob/master/ASAN_output.txt
An attacker can possibly use this flaw to execute arbitrary code.

Steps to reproduce:
Build latest php version (compile with ASAN)
Donwload PoC file called "stack_overflow" (see Test script)
Execute binary file in $WORKDIR/php-7.2.4/sapi/cli/:
$WORKDIR/php-7.2.4/sapi/cli/php stack_overflow

I was not able to reproduce this behavior when debugging with gdb.

Test script:
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PoC file can be found here: https://github.com/pnoltof/php_bug/blob/master/stack_overflow