CVE-2026-91990

High

Description

Tornado before 6.5.8 contains a memory amplification vulnerability in parse_multipart_form_data that splits multipart data before validating the max_parts limit. Attackers can send crafted multipart requests with many parts to create large transient lists, exhausting server memory and causing denial of service.

SeverityHigh

CVSS7.5

Exploit probability—

ProductTornado

PublishedSep 15, 2026

First seenSep 15, 2026

Weakness typeCWE-770Allocation of resources without limits

How to fix

Update

tornado6.5.8 or later

Vendor advisories

github.com/tornadoweb/tornado/security/advisories/GHSA-8423-8fgw-73vq

Affected products

Product	Affected versions	Fixed in
tornadoPyPI	v < 6.5.8	6.5.8

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