Nanopb is a small code-size Protocol Buffers implementation. When the compile time option PB_ENABLE_MALLOC is enabled, the message contains at least one field with FT_POINTER field type, custom stream callback is used with unknown stream length. and the pb_decode_ex() function is used with flag PB_DECODE_DELIMITED, then the pb_decode_ex() function does not automatically call pb_release(), like is done for other failure cases. This could lead to memory leak and potential denial-of-service. This vulnerability is fixed in 0.4.9.1.