S3QL before 2.27 mishandles checksumming, and consequently allows replay attacks in which an attacker who controls the backend can present old versions of the…

S3QL before 2.27 mishandles checksumming, and consequently allows replay attacks in which an attacker who controls the backend can present old versions of the filesystem metadata database as up-to-date, temporarily inject zero-valued bytes into files, or temporarily hide parts of files. This is related to the checksum_basic_mapping function.