CVE-2025-47287: Tornado vulnerable to excessive logging caused by malformed multipart form data
Description
Tornado is a Python web framework and asynchronous networking library. When Tornado's ``multipart/form-data`` parser encounters certain errors, it logs a warning but continues trying to parse the remainder of the data. This allows remote attackers to generate an extremely high volume of logs, constituting a DoS attack. This DoS is compounded by the fact that the logging subsystem is synchronous. All versions of Tornado prior to 6.5.0 are affected. The vulnerable parser is enabled by default. Upgrade to Tornado version 6.50 to receive a patch. As a workaround, risk can be mitigated by blocking `Content-Type: multipart/form-data` in a proxy.
Classification
CVE ID: CVE-2025-47287
CVSS Base Severity: HIGH
CVSS Base Score: 7.5
CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Affected Products
Vendor: tornadoweb
Product: tornado
Exploit Prediction Scoring System (EPSS)
EPSS Score: 0.12% (probability of being exploited)
EPSS Percentile: 32.18% (scored less or equal to compared to others)
EPSS Date: 2025-06-13 (when was this score calculated)
References
https://nvd.nist.gov/vuln/detail/CVE-2025-47287https://github.com/tornadoweb/tornado/security/advisories/GHSA-7cx3-6m66-7c5m
https://github.com/tornadoweb/tornado/commit/b39b892bf78fe8fea01dd45199aa88307e7162f3