Oniguruma through 6.9.3, as used in PHP 7.3.x and other products, has a heap-based buffer over-read in str_lower_case_match in regexec.c.An issue was discovered in Oniguruma 6.x before 6.9.4_rc2. In the function gb18030_mbc_enc_len in file gb18030.c, a UChar pointer is dereferenced without checking if it passed the end of the matched string. This leads to a heap-based buffer over-read.An issue was discovered in Oniguruma 6.x before 6.9.4_rc2. In the function fetch_interval_quantifier in regparse.c, PFETCH is called without checking PEND. This leads to a heap-based buffer over-read.