Unbound before 1.9.5 allows an integer overflow in sldns_str2wire_dname_buf_origin, leading to an out-of-bounds write.
There is no available reproducer or proof of concept for this issue, nor it was ever proven the buffer overflow can happen in practice. Indeed in the original report this issue was considered one that might not be triggered and for this reason its Impact is Moderate.
This issue has been addressed in the following products:
Red Hat Enterprise Linux 8
Via RHSA-2021:1853 https://access.redhat.com/errata/RHSA-2021:1853
This bug is now closed. Further updates for individual products will be reflected on the CVE page(s):