Description
Tornado is a Python web framework and asynchronous networking library. Versions 6.5.2 and below use an inefficient algorithm when parsing parameters for HTTP header values, potentially causing a DoS. The _parseparam function in httputil.py is used to parse specific HTTP header values, such as those in multipart/form-data and repeatedly calls string.count() within a nested loop while processing quoted semicolons. If an attacker sends a request with a large number of maliciously crafted parameters in a Content-Disposition header, the server's CPU usage increases quadratically (O(n²)) during parsing. Due to Tornado's single event loop architecture, a single malicious request can cause the entire server to become unresponsive for an extended period. This issue is fixed in version 6.5.3.
Problem types
CWE-400: Uncontrolled Resource Consumption
Product status
References
github.com/...ornado/security/advisories/GHSA-jhmp-mqwm-3gq8
github.com/...ommit/771472cfdaeebc0d89a9cc46e249f8891a6b29cd
github.com/tornadoweb/tornado/releases/tag/v6.5.3
Data based on CVE®. Copyright © 1999-2025, The MITRE Corporation. All rights reserved.
