tornado: multipart split() creates huge temp list before max_parts check -> memory amplification DoS (httputil.py:34) — GHSA-8423-8FGW-73VQ

Summary

## Description ### Summary `parse_multipart_form_data` (httputil.py:34) calls `data.split(b"--"+boundary+b"\r\n")` **before** the `max_parts` check (:35). A 600KB body with 100k parts creates a 100k-element transient list first, then rejects transient memory amplification (each split element is a copy). Pre-auth HTTP DoS. ### Root cause ```python parts = data[:final_boundary_index].split(b"--" + boundary + b"\r\n")…

Timeline

Published by source

2026-09-01

Risk context

• Reported severity or threat level: medium.
• Reported CVSS score: 6.9 out of 10.
• Review exposure for the affected product or family: pip: tornado.

Product

pip: tornado

What to do

General, cautious steps (verify details in the official source):

• Review exposure and plan remediation based on risk and environment.
• Identify affected product versions in your inventory and verify whether you are impacted.
• Apply vendor patches/updates or recommended mitigations as soon as available.
• Read the official advisory for exact affected versions and remediation steps.

Official advisory

• Read the official source

Evidence and provenance

Canonical advisory ID

GHSA-8423-8FGW-73VQ

Source

GitHub

Vendor

GitHub

Published by source

2026-09-01

Last source activity

2026-09-01

Curated by

hlukh.ch

Related advisories and connections

These advisories are connected by shared CVE, product, vendor, source, or time signals.