Sonatype Nexus Repository 3 allows an unauthenticated remote attacker to supply attacker-controlled input to a Java class loading call through an ExtDirect endpoint. This allows the attacker to learn whether specific classes are present in the application. The issue does not by itself allow code execution.
Use of Externally-Controlled Input to Select Classes or Code The product uses external input with reflection to select which classes or code to use, but it does not sufficiently prevent the input from selecting improper classes or code.