An issue was discovered in Oniguruma 6.2.0, as used in Oniguruma-mod in Ruby through 2.4.1 and mbstring in PHP through 7.1.5. A stack out-of-bounds read occurs in match_at() during regular expression searching. A logical error involving order of validation and access in match_at() could result in an out-of-bounds read from a stack buffer.

An issue was discovered in Oniguruma 6.2.0, as used in Oniguruma-mod in Ruby through 2.4.1 and mbstring in PHP through 7.1.5. A stack out-of-bounds write in onigenc_unicode_get_case_fold_codes_by_str() occurs during regular expression compilation. Code point 0xFFFFFFFF is not properly handled in unicode_unfold_key(). A malformed regular expression could result in 4 bytes being written off the end of a stack buffer of expand_case_fold_string() during the call to onigenc_unicode_get_case_fold_codes_by_str(), a typical stack buffer overflow.

An issue was discovered in Oniguruma 6.2.0, as used in Oniguruma-mod in Ruby through 2.4.1 and mbstring in PHP through 7.1.5. A heap out-of-bounds write or read occurs in next_state_val() during regular expression compilation. Octal numbers larger than 0xff are not handled correctly in fetch_token() and fetch_token_in_cc(). A malformed regular expression containing an octal number in the form of '\700' would produce an invalid code point value larger than 0xff in next_state_val(), resulting in an out-of-bounds write memory corruption.

An issue was discovered in Oniguruma 6.2.0, as used in Oniguruma-mod in Ruby through 2.4.1 and mbstring in PHP through 7.1.5. A stack out-of-bounds read occurs in mbc_enc_len() during regular expression searching. Invalid handling of reg->dmin in forward_search_range() could result in an invalid pointer dereference, as an out-of-bounds read from a stack buffer.

An issue was discovered in Oniguruma 6.2.0, as used in Oniguruma-mod in Ruby through 2.4.1 and mbstring in PHP through 7.1.5. A heap out-of-bounds write occurs in bitset_set_range() during regular expression compilation due to an uninitialized variable from an incorrect state transition. An incorrect state transition in parse_char_class() could create an execution path that leaves a critical local variable uninitialized until it's used as an index, resulting in an out-of-bounds write memory corruption.

An issue was discovered in Oniguruma 6.2.0, as used in Oniguruma-mod in Ruby through 2.4.1 and mbstring in PHP through 7.1.5. A SIGSEGV occurs in left_adjust_char_head() during regular expression compilation. Invalid handling of reg->dmax in forward_search_range() could result in an invalid pointer dereference, normally as an immediate denial-of-service condition.

A use-after-free in onig_new_deluxe() in regext.c in Oniguruma 6.9.2 allows attackers to potentially cause information disclosure, denial of service, or possibly code execution by providing a crafted regular expression. The attacker provides a pair of a regex pattern and a string, with a multi-byte encoding that gets handled by onig_new_deluxe(). Oniguruma issues often affect Ruby, as well as common optional libraries for PHP and Rust.

A NULL Pointer Dereference in match_at() in regexec.c in Oniguruma 6.9.2 allows attackers to potentially cause denial of service by providing a crafted regular expression. Oniguruma issues often affect Ruby, as well as common optional libraries for PHP and Rust.

Oniguruma before 6.9.3 allows Stack Exhaustion in regcomp.c because of recursion in regparse.c.

An integer overflow in the search_in_range function in regexec.c in Oniguruma 6.x before 6.9.4_rc2 leads to an out-of-bounds read, in which the offset of this read is under the control of an attacker. (This only affects the 32-bit compiled version). Remote attackers can cause a denial-of-service or information disclosure, or possibly have unspecified other impact, via a crafted regular expression.

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 (formerly known as fetch_range_quantifier) in regparse.c, PFETCH is called without checking PEND. This leads to a heap-based buffer over-read.

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.