In the GNU C Library (aka glibc or libc6) before 2.28, parse_reg_exp in posix/regcomp.c misparses alternatives, which allows attackers to cause a denial of service (assertion failure and application exit) or trigger an incorrect result by attempting a regular-expression match.
CREATE(Triage): {Link=https://nvd.nist.gov/vuln/detail/CVE-2009-5155 User=admin}
