Decompression is the process of restoring compressed data to its original form. Software does this when it unpacks archives, decodes media, or expands network payloads. In security-sensitive code, decompression often happens on attacker-controlled input, which means the parser must trust as little as possible until sizes, offsets, and integrity checks are validated.
This matters because decompression code frequently allocates memory and copies bytes. If it miscalculates a length, follows a malformed structure, or accepts inconsistent metadata, the result can be buffer overflows, out-of-bounds reads, or denial of service. Defenders treat decompression routines as high-risk attack surface, so they use sandboxing, fuzz testing, strict format validation, and prompt patching. Even a simple archive can become dangerous if the decompressor mishandles it.