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Use-after-free in extract() with EXTR_REFS #18211

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Use-after-free in extract() with EXTR_REFS #18211

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4 changes: 3 additions & 1 deletion ext/standard/array.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1863,8 +1863,10 @@ static zend_long php_extract_ref_overwrite(zend_array *arr, zend_array *symbol_t
} else {
ZVAL_MAKE_REF_EX(entry, 2);
}
zval_ptr_dtor(orig_var);
zval garbage;
ZVAL_COPY_VALUE(&garbage, orig_var);
ZVAL_REF(orig_var, Z_REF_P(entry));
zval_ptr_dtor(&garbage);
} else {
if (Z_ISREF_P(entry)) {
Z_ADDREF_P(entry);
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23 changes: 23 additions & 0 deletions ext/standard/tests/gh18209.phpt
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@@ -0,0 +1,23 @@
--TEST--
GH-18209: Use-after-free in extract() with EXTR_REFS
--CREDITS--
Noam Rathaus (nrathaus)
--FILE--
<?php

class C {
public function __destruct() {
var_dump($GLOBALS['b']);
$GLOBALS['b'] = 43;
}
}

$b = new C;
$array = ['b' => 42];
extract($array, EXTR_REFS);
var_dump($b);

?>
--EXPECT--
int(42)
int(43)
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