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use-after-free when an error handler removes a failing zlib.inflate filter - #24176
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…te filter The filter raised its notice and then reset its state; an error handler that removed the filter had freed that state by then.
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devnexen
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Oct 7, 2026
LamentXU123
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* PHP-8.6: Fix use-after-free when removing a failing zlib.inflate filter (#24176)
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* PHP-8.4: Fix use-after-free when removing a failing zlib.inflate filter (php#24176)
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* PHP-8.5: Fix use-after-free when removing a failing zlib.inflate filter (php#24176)
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On a corrupt input
zlib.inflateraisesE_NOTICE("zlib: data error") and then resets its input pointers. A user error handler that callsstream_filter_remove()on that filter frees the filter's state first, so the reset writes to freed memory (Valgrind: invalid writes inphp_zlib_inflate_filter()). The fix resets the state before raising the notice; nothing touches the filter after it.Test:
ext/zlib/tests/zlib_filter_inflate_error_handler_removes_filter.phpt, as a write and as a read filter.Not covered, same family: an error handler that closes the stream itself during any filter's diagnostic (
fclose()is only refused while a user filter runs), which would needPHP_STREAM_FLAG_NO_FCLOSEaround the whole filter chain walk.