CVE-2025-67726

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.

CVSS v3 7.5 HIGH

7.5^/10

CVSS v3 : HIGH

Vector :

Exploitability : 3.9 / Impact : 3.6

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction NONE

Confidentiality Impact NONE

Integrity Impact NONE

Availability Impact HIGH

Scope UNCHANGED

References

Link	Resource
https://github.com/tornadoweb/tornado/commit/771472cfdaeebc0d89a9cc46e249f8891a6b29cd	Patch
https://github.com/tornadoweb/tornado/releases/tag/v6.5.3	Release Notes
https://github.com/tornadoweb/tornado/security/advisories/GHSA-jhmp-mqwm-3gq8	Vendor Advisory

Configurations

Configuration 1 (hide)

cpe:2.3:a:tornadoweb:tornado:*:*:*:*:*:*:*:*

History

No history.

Information

Published : 2025-12-12 07:15

Updated : 2025-12-22 18:56

NVD link : CVE-2025-67726

Mitre link : CVE-2025-67726

CVE.ORG link : CVE-2025-67726

JSON object : View

Products Affected

tornadoweb

tornado

CWE

CWE-400

Uncontrolled Resource Consumption

CWE-834

Excessive Iteration

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