Goal Reached Thanks to every supporter — we hit 100%!

Goal: 1000 CNY · Raised: 1359 CNY

100%
Buy Us a Coffee

CVE-2026-82397— Tornado: Urlencoded body parsing omits max_num_fields, so one request can stall the event loop

Quick assessment

Affected
tornadoweb tornado
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

tornadoweb tornado是tornadoweb团队开源的一个高性能非阻塞Web服务器框架。 tornadoweb tornado 6.5.8之前版本存在安全漏洞，该漏洞源于解析application/x-www-form-urlencoded请求体时未传递max_num_fields参数限制字段数量，可能导致未经身份验证的攻击者通过发送包含数百万分隔字段的请求体同步阻塞单线程事件循环，延迟每个连接，造成拒绝服务。

CVSS 7.5 · High EPSS 0.35% · P27

Affected Version Matrix 1

VendorProduct Version RangeStatus
tornadoweb tornado < 6.5.8 affected
Get alerts for future matching vulnerabilities Log in to subscribe

I. Basic Information for CVE-2026-82397

Vulnerability Information
Have questions about the vulnerability? See if Shenlong's analysis helps!
View Shenlong Deep Dive ↗

Although we use advanced large model technology, its output may still contain inaccurate or outdated information.Shenlong tries to ensure data accuracy, but please verify and judge based on the actual situation.

Vulnerability Title
Tornado: Urlencoded body parsing omits max_num_fields, so one request can stall the event loop
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
未加控制的资源消耗(资源穷尽)
Source: CVE Program / CVE List V5
Vulnerability Title
tornadoweb tornado 输入验证错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
tornadoweb tornado是tornadoweb团队开源的一个高性能非阻塞Web服务器框架。 tornadoweb tornado 6.5.8之前版本存在安全漏洞，该漏洞源于解析application/x-www-form-urlencoded请求体时未传递max_num_fields参数限制字段数量，可能导致未经身份验证的攻击者通过发送包含数百万分隔字段的请求体同步阻塞单线程事件循环，延迟每个连接，造成拒绝服务。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
tornadoweb tornado < 6.5.8 -

II. Public POCs for CVE-2026-82397

# POC Description Source Link Shenlong Link
AI-Generated POC Premium

No public POC found.

Login to generate AI POC

III. Intelligence Information for CVE-2026-82397

请登录查看更多情报信息。

Patches & Fixes for CVE-2026-82397 (2)

Vendor Advisories for CVE-2026-82397 (1)

Vendor Pages for CVE-2026-82397 (1)

IV. Related Vulnerabilities

Same product: tornado
Same vendor: tornadoweb
Same weakness: CWE-400

V. Comments for CVE-2026-82397

No comments yet

Leave a comment