In the GNU C Library (aka glibc or libc6) through 2.29, proceed_next_node in posix/regexec.c has a heap-based buffer over-read via an attempted case-insensitive regular-expression match.
https://www.oracle.com/security-alerts/cpuapr2022.html
https://usn.ubuntu.com/4416-1/
https://support.f5.com/csp/article/K54823184
https://sourceware.org/bugzilla/show_bug.cgi?id=24114
https://security.netapp.com/advisory/ntap-20190315-0002/
https://security.gentoo.org/glsa/202006-04
https://kc.mcafee.com/corporate/index?page=content&id=SB10278
https://debbugs.gnu.org/cgi/bugreport.cgi?bug=34142