standard: Pass unserialize('') through the regular path - #23827
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Previously `unserialize()` with an empty string as input was handled specially, returning `false` (indicating an error), but without emitting an associated warning. We can just pass it through the regular path, which will also return `false` (including the warning) and will also avoid a check that is almost never taken in practice. Fixes php#23780.
ndossche
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Sep 21, 2026
| HashTable *class_hash = NULL, *prev_class_hash; | ||
| zend_long prev_max_depth, prev_cur_depth; | ||
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| if (buf_len == 0) { |
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This rings a bell though. I think I recall a case somewhere in the codebase wshere a non-null terminated string was passed to unserialize; that might need fixing (if it's still there and my memory serves me well) before proceeding with this.
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php_unserialize_with_options() is only ever called from:
phar_metadata_tracker_unserialize_or_copy()PHP_FUNCTION(unserialize)
in both cases the input is a zend_string which would already be malformed when not terminated. And php_var_unserialize_internal() also immediately bails out when YYCURSOR >= YYLIMIT, which is the case for an empty input.
So this should be safe.
ndossche
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Sep 22, 2026
TimWolla
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Sep 22, 2026
* PHP-8.6:
standard: Pass `unserialize('')` through the regular path (#23827)
sebastianbergmann
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Sep 23, 2026
As of php/php-src#23827, unserialize('') emits a warning, which our error handler converts to an exception
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Previously
unserialize()with an empty string as input was handled specially, returningfalse(indicating an error), but without emitting an associated warning. We can just pass it through the regular path, which will also returnfalse(including the warning) and will also avoid a check that is almost never taken in practice.Fixes #23780.