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Not in CISA KEV
HIGH severity

Tornado vulnerable to excessive logging caused by malformed multipart form dataGHSA-7cx3-6m66-7c5m

HIGHFix: tornadoweb/tornado@b39b892

GHSA-7cx3-6m66-7c5m is a high-severity (CVSS 7.5) CWE-770 vulnerability in tornado. A fix is available for tornado — see the affected versions and patch details below.

Also known asCVE-2025-47287PYSEC-2026-1974
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Nov 10, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
  • CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for GHSA-7cx3-6m66-7c5m.

EPSS Exploitation Probability

via FIRST.org ↗
0.7%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs55th percentile — riskier than 55% of all scored CVEsHighest risk
0.17%0.67%1.16%1.66%1.2%0.7%May 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected
🐍tornado

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.

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.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🐍PyPItornadoall versions6.5pip install --upgrade 'tornado==6.5'

Affected Products

2 products · 2 configurations
OS
debian linuxdebian
1 version
11.0
Application
tornadotornadoweb
< 6.5.0
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for tornado, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update tornado to 6.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-7cx3-6m66-7c5m is resolved across your whole dependency graph.

  3. Workarounds

    Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatImportant

This vulnerability marked as Important because it leverages the synchronous nature of the logging subsystem to induce a DoS condition. Specifically, malformed multipart/form-data payloads cause repeated, blocking log writes, which stall the event loop that underpins Tornado’s asynchronous architecture. Furthermore,…

Workaround published by Red Hat
No mitigation is currently available that meets Red Hat Product Security’s standards for usability, deployment, applicability, or stability.
Source: Red Hat security advisory for GHSA-7cx3-6m66-7c5m (CC BY 4.0)
ProductFixed inAdvisory
Red Hat Enterprise Linux 10python-tornado-0:6.4.2-1.el10_0.1RHSA-2025:8135
Red Hat Enterprise Linux 7 Extended Lifecycle Supportpython-tornado-0:4.2.1-5.el7_9.1RHSA-2025:8664
Red Hat Enterprise Linux 8pcs-0:0.10.18-2.el8_10.5RHSA-2025:8254
Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Supportpcs-0:0.10.8-1.el8_4.7RHSA-2025:8323
Red Hat Enterprise Linux 8.6 Telecommunications Update Servicepcs-0:0.10.12-6.el8_6.8RHSA-2025:8290
Red Hat Enterprise Linux 8.8 Extended Update Supportpcs-0:0.10.15-4.el8_8.6RHSA-2025:8279
Red Hat Enterprise Linux 9python-tornado-0:6.4.2-2.el9_6.2RHSA-2025:8136
Red Hat Enterprise Linux 9.0 Update Services for SAP Solutionspcs-0:0.11.1-10.el9_0.8RHSA-2025:8291

Frequently Asked Questions

### Summary 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. ### Affected versions All versions of Tornado prior to 6.5 are affected. The vulnerable parser is enabled by default. ### Solution Upgrade to Tornado version 6.5. In the meantime, risk can be mitigated by blocking `Content-Type: multipart/form-data` in a
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Tornado vulnerable to excessive logging caused by…