Tornado: Event loop blocking and excess memory use from chunked bodies with many small chunks

[ Description ]Official description

Tornado is a Python web framework and asynchronous networking library. Prior to 6.6.0, Tornado decodes HTTP/1.1 chunked transfer encoding by processing body data that has already arrived without yielding to the event loop. A remote unauthenticated peer can send millions of one-byte chunks to monopolize the process event loop and stall every other connection served by that process, while lowering max_body_size only limits the duration of each request. For handlers that do not use @stream_request_body, retaining each chunk as a separate object can consume roughly twenty times the received body size, and SimpleAsyncHTTPClient has the same event-loop behavior when reading a response from a malicious server. This issue is fixed in version 6.6.0.

[ Fixes ]Fixes and patches

• tornado 6.6Fixed version · GitHub Advisories · pip package tornado: upgrade to 6.6 or later (affected < 6.6)

[ Packages ]Affected open-source packages

• tornado pipAffected < 6.6 · fixed in 6.6 · GHSA-r4j5-9xpp-3985

[ References ]References

• github.com/tornadoweb/tornado/commit/ceab33581489751a66fba8566ad6d5960d4b01c8
• github.com/tornadoweb/tornado/pull/3773
• github.com/tornadoweb/tornado/releases/tag/v6.6.0
• github.com/tornadoweb/tornado/security/advisories/GHSA-r4j5-9xpp-3985