parsedmarc before 11.0.1 decompresses gzip and ZIP attachments in a single unbounded read with no limit on decompressed output size. Because parsedmarc automatically processes incoming DMARC report emails without user interaction, an unauthenticated remote attacker can send a crafted email with a highly compressed attachment to the monitored mailbox, causing the parsedmarc process to allocate memory proportional to the uncompressed size and exhaust available RAM.