CVE-2026-49854: Tornadoweb Tornado

Medium severity, CVSS 5.3. EPSS: 0.4% chance of exploitation in the next 30 days.

Tornado is a Python web framework and asynchronous networking library. Prior to 6.5.6, the optional native extension tornado.speedups implemented websocket_mask without validating that the mask argument is exactly four bytes, allowing the C function to read up to three bytes beyond the provided buffer when reached through Tornado XSRF token decoding with the native extension active. This issue is fixed in version 6.5.6.

Affected products

• Tornadoweb Tornado: before 6.5.6 (fixed in 6.5.6)

Published 2026-07-14. Last modified 2026-07-15.