In the GNU C Library (aka glibc or libc6) through 2.29, check_dst_limits_calc_pos_1 in posix/regexec.c has Uncontrolled Recursion, as demonstrated by '(\227|)(\\1\\1|t1|\\\2537)+' in grep.
CREATE(Triage): {Link=https://nvd.nist.gov/vuln/detail/CVE-2018-20796 User=admin}
