CVE-2025-67726 (GCVE-0-2025-67726)
Vulnerability from cvelistv5
Published
2025-12-12 06:13
Modified
2025-12-18 18:48
Severity ?
7.5 (High) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CWE
  • CWE-834 - Excessive Iteration
  • CWE-400 - Uncontrolled Resource Consumption
Summary
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.
References
Impacted products
Vendor Product Version
tornadoweb tornado Version: < 6.5.3
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