AIKIDO-2026-945215
tornado is vulnerable to Denial of Service (DoS)
53
Medium Risk
This Affects:
tornadoTL;DR
HTTPServerRequest parses URL query strings with parse_qs_bytes and no field-count limit, even though the POST body path already rejects more than 1000 application/x-www-form-urlencoded fields. A GET whose query string is packed with thousands of short fields still fits under max_header_size and is parsed synchronously on the IOLoop, stalling other connections on that loop. The fix applies the same max_arguments cap to query strings and returns 400 once the limit is exceeded.
Who does this affect?
You are affected if you are using a version that falls within the vulnerable range and use Tornado as an HTTP server.
Background info
tornado is vulnerable to Denial of Service (DoS) in versions 0.2 - 6.5.8.
How to fix this
Upgrade the tornado library to the patch version.
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