AIKIDO-2026-819522
tornado is vulnerable to Denial of Service
75
High Risk
This Affects:
tornadoTL;DR
The HTTPHeaders.add method in Tornado accumulates values using string concatenation when the same header name is repeated. Due to Python string immutability, each concatenation copies the entire string, resulting in O(n^2) time complexity. Given Tornado's single event loop architecture, a single maliciously crafted HTTP request can block the server's event loop for an extended period, causing a Denial of Service (DoS).
Who does this affect?
You are affected if you are using a version that falls within the vulnerable range.
Background info
tornado is vulnerable to Denial of Service in versions 0.0.0 - 6.5.2.
How to fix this
Upgrade the tornado library to the patch version.
Links
GitHub Release
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SOC 2Compliant
ISO 27001Compliant