# CVE-2026-82397 — tornadoweb tornado

> As of 2026-08-31, CVE-2026-82397 is a HIGH-severity vulnerability in tornadoweb tornado, CVSS v3.1 7.5, EPSS 0.3% (27.8th percentile). No Threadlinqs-tracked threat campaign has been attributed to CVE-2026-82397 as of 2026-08-31; the identifier is re-checked against the Threadlinqs threat corpus on every daily ingest.

**Last updated:** 2026-08-31

## What is CVE-2026-82397?

Tornado is a Python web framework and asynchronous networking library. Prior to 6.5.8, Tornado parses application/x-www-form-urlencoded request bodies with urllib.parse.parse_qs in tornado/escape.py without passing max_num_fields. RequestHandler._execute in tornado/web.py parses the body before handler dispatch through HTTPServerRequest._parse_body and parse_body_arguments in tornado/httputil.py, so an unauthenticated request body containing millions of separator-delimited fields can synchronously stall the single-threaded event loop and delay every connection. The body is bounded only by max_buffer_size, which defaults to 104857600 bytes. This issue is fixed in version 6.5.8.

The record classifies CVE-2026-82397 under weakness classes [CWE-400](https://intel.threadlinqs.com/cwe/CWE-400), [CWE-1284](https://intel.threadlinqs.com/cwe/CWE-1284). Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs no prior authentication, needs no user interaction, and has high impact on availability. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 35 days ago.

## Severity and exploitation probability

- **CVSS v3.1 base score:** 7.5 — HIGH (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **EPSS (FIRST):** 0.3% probability of exploitation in the next 30 days, higher than 27.8% of all scored CVEs
- **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog
- **Threadlinqs priority:** 4.9/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- **Published:** 2026-08-31

## Is CVE-2026-82397 being exploited?

It currently carries a trending score of 36 in the Threadlinqs vulnerability feed.

## Affected products and versions

- **tornadoweb**: tornado

## How to fix CVE-2026-82397

No vendor patch reference has been recorded for CVE-2026-82397 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.

## Threat activity tracking CVE-2026-82397

No threat campaign in the Threadlinqs corpus currently references CVE-2026-82397, in its CVE list or as an indicator. The linkage is recomputed from the live corpus on every daily ingest, so this section fills in as soon as a tracked campaign cites the identifier.

## Sources

Enriched from CVE.org, NVD, FIRST EPSS. Last verified by Threadlinqs on 2026-09-02. This product uses the NVD API but is not endorsed or certified by the NVD.

**Vendor advisory and patch**

- [github.com](https://github.com/tornadoweb/tornado/security/advisories/GHSA-mpf4-983q-p7j4)

**Other references**

- [github.com](https://github.com/tornadoweb/tornado/pull/3704)
- [github.com (8d6363ed7b69d5f0da806efe34d256627a2191de)](https://github.com/tornadoweb/tornado/commit/8d6363ed7b69d5f0da806efe34d256627a2191de)
- [github.com (v6.5)](https://github.com/tornadoweb/tornado/releases/tag/v6.5.8)

Canonical: https://intel.threadlinqs.com/cve/CVE-2026-82397
Full detection coverage and IOCs for threats exploiting CVE-2026-82397 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp