Acrobat Reader DC versions 2021.005.20054 (and earlier), 2020.004.30005 (and earlier) and 2017.011.30197 (and earlier) are affected by a Null pointer dereference vulnerability. An authenticated attacker could leverage this vulnerability achieve an application denial-of-service in the context of the current user. Exploitation of this issue does not requires user interaction.
https://helpx.adobe.com/security/products/acrobat/apsb21-51.html