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CVE-2026-31958— Tornado has a DoS due to too many multipart parts

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.

Tornado是中国龙卷风科技（Tornado）社区的一个Python Web框架和异步网络库。该库通过使用非阻塞网络I / O，可以扩展到成千上万的开放连接，使其非常适合 长时间轮询， WebSocket和其他需要与每个用户建立长期连接的应用程序。 Tornado 6.5.5之前版本存在资源管理错误漏洞，该漏洞源于解析多部分表单数据时缺少部分数量限制，可能导致拒绝服务攻击。

AI Predicted 5.3 Difficulty: Easy EPSS 0.49% · P40

Possible ATT&CK Techniques 1 AI

T1499 · Endpoint Denial of Service
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I. Basic Information for CVE-2026-31958

Vulnerability Information
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Vulnerability Title
Tornado has a DoS due to too many multipart parts
Source: CVE Program / CVE List V5
Vulnerability Description
Tornado is a Python web framework and asynchronous networking library. In versions of Tornado prior to 6.5.5, the only limit on the number of parts in multipart/form-data is the max_body_size setting (default 100MB). Since parsing occurs synchronously on the main thread, this creates the possibility of denial-of-service due to the cost of parsing very large multipart bodies with many parts. This vulnerability is fixed in 6.5.5.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
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
Tornado 资源管理错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Tornado是中国龙卷风科技（Tornado）社区的一个Python Web框架和异步网络库。该库通过使用非阻塞网络I / O，可以扩展到成千上万的开放连接，使其非常适合 长时间轮询， WebSocket和其他需要与每个用户建立长期连接的应用程序。 Tornado 6.5.5之前版本存在资源管理错误漏洞，该漏洞源于解析多部分表单数据时缺少部分数量限制，可能导致拒绝服务攻击。
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 < 6.5.5 -

II. Public POCs for CVE-2026-31958

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III. Intelligence Information for CVE-2026-31958

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Vendor Advisories for CVE-2026-31958 (1)

IV. Related Vulnerabilities

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

V. Comments for CVE-2026-31958

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