# Tornado: Urlencoded body parsing omits max_num_fields, so one request can stall the event loop

Advisory record · `GHSA-mpf4-983q-p7j4`

- **Identifiers:** `GHSA-mpf4-983q-p7j4` · `CVE-2026-82397` · `PYSEC-2026-3928`
- **State:** Confirmed
- **Severity:** CVSS 7.5 High
- **Critical:** No
- **Weakness (CWE):** [CWE-400](https://cwe.mitre.org/data/definitions/400.html) · [CWE-1284](https://cwe.mitre.org/data/definitions/1284.html)
- **Tags:** [Denial of service](https://agentprime.io/advisories/tag/dos.md) · [CWE-1284](https://agentprime.io/advisories/tag/cwe-1284.md)
- **Published:** 2 Sept 2026
- **Updated:** 10 Sept 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 2 Sept 2026, 14:38 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `tornado` (PyPI): affected `<6.5.8`; fixed in `6.5.8`

## Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

## Severity and exploitation

- 7.5 High, CVSS 3.1: `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`, from CNA (GitHub_M)

- **CISA KEV:** Not listed.
- **EPSS:** 0.0035, the 28th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

- 31 Oct 2026, 14:10 UTC: First seen by agentprime
- 31 Oct 2026, 14:10 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-mpf4-983q-p7j4)

## Sources

- [GitHub Advisory Database: GHSA-mpf4-983q-p7j4](https://github.com/advisories/GHSA-mpf4-983q-p7j4)
- [OSV: GHSA-mpf4-983q-p7j4](https://osv.dev/vulnerability/GHSA-mpf4-983q-p7j4)
- <https://github.com/tornadoweb/tornado/security/advisories/GHSA-mpf4-983q-p7j4>
- <https://nvd.nist.gov/vuln/detail/CVE-2026-82397>
- <https://github.com/tornadoweb/tornado/pull/3704>
- <https://github.com/tornadoweb/tornado/commit/8d6363ed7b69d5f0da806efe34d256627a2191de>
- <https://github.com/tornadoweb/tornado>
- <https://github.com/tornadoweb/tornado/releases/tag/v6.5.8>

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.

## Check whether this affects you

A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: <https://agentprime.io/mcp.md>
- In a browser: <https://agentprime.io/check/> reads your lockfile in the browser, never uploading it.
- Whether it touches your code, with file and line: the Claude Code plugin, <https://agentprime.io/plugin.md>
- As JSON: <https://api.agentprime.io/v1/advisories/GHSA-mpf4-983q-p7j4>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

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The web page: <https://agentprime.io/advisories/GHSA-mpf4-983q-p7j4/>. Everything for agents: <https://agentprime.io/llms.txt>.