CVE-2021-21426
Magento-lts is a long-term support alternative to Magento Community Edition (CE). In magento-lts versions 19.4.12 and prior and 20.0.8 and prior, there is a vulnerability caused by the unsecured deserialization of an object. A patch in versions 19.4.13 and 20.0.9 was back ported from Zend Framework 3. The vulnerability was assigned CVE-2021-3007 in Zend Framework.
Source: CVE-2021-21426