Stop grapheme_strrev from using UBRK_DONE as a byte index - #23323
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ubrk_previous() returns UBRK_DONE after the first boundary. The loop condition ran before that assignment, so the body treated -1 as an offset and wrote into the zend_string NUL. Break when the iterator is done, and NUL-terminate the result of zend_string_alloc.
devnexen
approved these changes
Aug 16, 2026
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grapheme_strrev() called ubrk_previous() inside a loop whose condition still saw the previous position, so UBRK_DONE (-1) was used as a byte offset and overwrote the result NUL. Stop when the iterator is done, and NUL-terminate the zend_string_alloc() buffer.