The "fluent-plugin-s3" plugin (specifically the "in_s3" input plugin) supports reading and decompressing heavily compressed files (such as "gzip", "lzma2", and "lzop") from Amazon S3. It was discovered that the plugin read the entire decompressed payload into memory at once without enforcing a strict size limit. If an attacker has sufficient permissions to upload files to the monitored S3 bucket, they can upload a maliciously crafted, highly compressed file. When Fluentd attempts to decompress this file, it will expand to an excessive size and it will consume significant system resources.