Vulnerability 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.
CVSS Score
HIGH
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Tornadoweb | Tornado | < 6.5.3 |
Related Weaknesses (CWE)
References
- https://github.com/tornadoweb/tornado/commit/771472cfdaeebc0d89a9cc46e249f8891a6Patch
- https://github.com/tornadoweb/tornado/releases/tag/v6.5.3Release Notes
- https://github.com/tornadoweb/tornado/security/advisories/GHSA-jhmp-mqwm-3gq8Vendor Advisory
FAQ
What is CVE-2025-67726?
CVE-2025-67726 is a vulnerability with a CVSS score of 7.5 (HIGH). 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. ...
How severe is CVE-2025-67726?
CVE-2025-67726 has been rated HIGH with a CVSS base score of 7.5/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2025-67726?
Check the references section above for vendor advisories and patch information. Affected products include: Tornadoweb Tornado.