An issue has been found in dnsdist in the way EDNS0 OPT records are handled when parsing responses from a backend. When dnsdist is configured to add EDNS Client Subnet to a query, the response may contain an EDNS0 OPT record that has to be removed before forwarding the response to the initial client. On a 32-bit system, the pointer arithmetic used when parsing the received response to remove that record might trigger an undefined behavior leading to a crash.
dnsdist up to and including 1.1.0 is affected on 32-bit systems. dnsdist 1.2.0 is not affected, dnsdist on 64-bit systems is not affected.
Created dnsdist tracking bugs for this issue:
Affects: epel-7 [bug 1483873]
Affects: fedora-all [bug 1483872]
This was fixed in dnsdist-1.2.0-1.el7 and dnsdist-1.2.0-1.fc26