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…d \k<name> When a \\k<name> backref in an mb_ereg_replace() replacement string lacks its closing delimiter, the error path computed p = name_end + 1 past eos and copied the trailing NUL terminator into the output; the multibyte sibling path (p += clen after \\k) could overshoot eos and read heap bytes past the string. Both paths are now clamped to eos so verbatim fallback never copies beyond the parsed name. Sibling audit found no other copies past eos in this loop.
youkidearitai
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Sep 1, 2026
youkidearitai
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youkidearitai
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Thank you, LGTM.
I confirmed that there is null byte before fix this.
before
$ sapi/cli/php -r "var_dump(bin2hex(mb_ereg_replace('(\d+)', '\k<num', '123')));"
string(14) "5c6b3c6e756d00"
after
$ sapi/cli/php -r "var_dump(bin2hex(mb_ereg_replace('(\d+)', '\k<num', '123')));"
string(12) "5c6b3c6e756d"
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When a
\k<name>backreference in an mb_ereg_replace() replacement string lacks its closing delimiter, the verbatim copy of the escape sequence measured its length from a pointer one past the string end and embedded the trailing NUL terminator in the replacement output, and the multibyte scan of the name after\kcould equally read heap bytes beyond the string end. Both copy lengths are now clamped to the string end, so neither runs past the parsed name. A regression test covers the unterminated-name and multibyte cases.