---
title: "CVE-2026-91990: Tornado - Denial of Service"
description: "Tornado < 6.5.8 contains a denial of service vulnerability caused by improper validation of max_parts in parse_multipart_form_data, letting attackers exhaust server memory via crafted multipart requests, exploit requires no special privileges."
url: https://panop.io/threat-heartbeat/CVE-2026-91990/
---

# CVE-2026-91990 Tornado - Denial of Service

Tornado < 6.5.8 contains a denial of service vulnerability caused by improper validation of max\_parts in parse\_multipart\_form\_data, letting attackers exhaust server memory via crafted multipart requests, exploit requires no special privileges.

CVSS base score 7.5 /10

High

CISA KEV

Not listed

Public exploit

None known

Authentication

Not required

EPSS

0.42% chance of exploitation in 30 days

[View the NVD record ↗](https://nvd.nist.gov/vuln/detail/CVE-2026-91990)

## Details

Type

Denial of Service

Impact

Denial Of Service

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Published

15 September 2026

Updated

15 October 2026

Weakness

[CWE-770](https://cwe.mitre.org/data/definitions/770.html)

## Vendor fix

Update to version 6.5.8 or later.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

## References

- [https://nvd.nist.gov/vuln/detail/CVE-2026-91990](https://nvd.nist.gov/vuln/detail/CVE-2026-91990)
- [https://www.vulncheck.com/advisories/tornado-before-6.5.8-memory-amplification-dos-via-multipart](https://www.vulncheck.com/advisories/tornado-before-6.5.8-memory-amplification-dos-via-multipart)
- [https://github.com/tornadoweb/tornado/security/advisories/GHSA-8423-8fgw-73vq](https://github.com/tornadoweb/tornado/security/advisories/GHSA-8423-8fgw-73vq)

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## What this record can't tell you

- Whether you run the affected software, and where
- Whether an attacker can actually reach and exploit it
- The misconfigurations that never get a CVE number
- What it would cost the business, ranked into what to fix first

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