CVE-2026-91990: Tornadoweb Tornado

High severity, CVSS 7.5. EPSS: 0.4% chance of exploitation in the next 30 days.

Tornado before 6.5.8 contains a memory amplification vulnerability in parse_multipart_form_data that splits multipart data before validating the max_parts limit. Attackers can send crafted multipart requests with many parts to create large transient lists, exhausting server memory and causing denial of service.

Affected products

• Tornadoweb Tornado: before 6.5.8 (fixed in 6.5.8)

Published 2026-09-15. Last modified 2026-09-16.