CVE-2020-26159 was determined to not be a vulnerability and was rejected. As a result, the previously applied patch to address CVE-2020-26159 has been reverted. The additional fixes which were included in ELA-292-1 remain in place.
For Debian 8 jessie, these problems have been fixed in version 5.9.5-3.2+deb8u6.
We recommend that you upgrade your libonig packages.
Further information about Extended LTS security advisories can be found at: https://deb.freexian.com/extended-lts/