Memory corruption via undersized VZT dictionary allocation

Integer overflow in GTKWave's VZT dictionary decoder in version 3.3.115 allows context-dependent attackers to corrupt memory via a crafted file. vzt_rd_block_vch_decode multiplies attacker-controlled num_sections and num_dict_entries values when allocating val_dict, so overflow creates an undersized heap buffer that the decoder writes past. Exploitation requires an RLE-encoded VZT block with reversed time bounds and a victim to open the file; the demonstrated consequence is an out-of-bounds heap write, while code execution depends on threading and heap behavior.