CVE-2025-54121— Starlette has possible denial-of-service vector when parsing large files in multipart forms
Quick assessment
Affected
encode starlette
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.
Starlette是Encode开源的一个轻量级的 ASGI 框架/工具包。非常适合用 Python 构建异步 web 服务。 Starlette 0.47.1及之前版本存在安全漏洞，该漏洞源于对多部分表单处理不当，可能导致拒绝服务攻击。
Possible ATT&CK Techniques 1 AI
T1499 · Endpoint Denial of Service
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I. Basic Information for CVE-2025-54121
Vulnerability Information
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Vulnerability Title
Starlette has possible denial-of-service vector when parsing large files in multipart forms
Source: CVE Program / CVE List V5
Vulnerability Description
Starlette is a lightweight ASGI (Asynchronous Server Gateway Interface) framework/toolkit, designed for building async web services in Python. In versions 0.47.1 and below, when parsing a multi-part form with large files (greater than the default max spool size) starlette will block the main thread to roll the file over to disk. This blocks the event thread which means the application can't accept new connections. The UploadFile code has a minor bug where instead of just checking for self._in_memory, the logic should also check if the additional bytes will cause a rollover. The vulnerability is fixed in version 0.47.2.
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:L
Source: CVE Program / CVE List V5
Vulnerability Type
不加限制或调节的资源分配
Source: CVE Program / CVE List V5
Vulnerability Title
Starlette 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Starlette是Encode开源的一个轻量级的 ASGI 框架/工具包。非常适合用 Python 构建异步 web 服务。 Starlette 0.47.1及之前版本存在安全漏洞，该漏洞源于对多部分表单处理不当，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
II. Public POCs for CVE-2025-54121
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News Coverage for CVE-2025-54121 (1)
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V. Comments for CVE-2025-54121
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