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CVE-2026-54283— Starlette: request.form() limits silently ignored for application/x-www-form-urlencoded enable DoS

CVSS 7.5 · High EPSS 0.40% · P33

Possible ATT&CK Techniques 1AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 1

VendorProductVersion RangeStatus
Kludexstarlette>= 0.4.1, < 1.3.1affected
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I. Basic Information for CVE-2026-54283

Vulnerability Information
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Vulnerability Title
Starlette: request.form() limits silently ignored for application/x-www-form-urlencoded enable DoS
Source: CVE Program / CVE List V5
Vulnerability Description
Starlette is a lightweight ASGI framework/toolkit. From 0.4.1 until 1.3.1, request.form() accepts max_fields and max_part_size to bound resource consumption while parsing form data. These limits are enforced for multipart/form-data, but silently ignored for application/x-www-form-urlencoded. An unauthenticated attacker can therefore send a urlencoded body with an arbitrarily large number of fields or an arbitrarily large field, even when the application configured limits it believed would apply. This vulnerability is fixed in 1.3.1.
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
不加限制或调节的资源分配
Source: CVE Program / CVE List V5
Vulnerability Title
Marcelo Trylesinski Starlette 资源管理错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Marcelo Trylesinski Starlette是Marcelo Trylesinski个人开发者的一款轻量级异步Web框架工具。 Marcelo Trylesinski Starlette 0.4.1版本至1.3.1之前版本存在资源管理错误漏洞，该漏洞源于在解析表单数据时，针对application/x-www-form-urlencoded类型的请求未正确限制字段数量和大小，可能导致未经身份验证的攻击者发送大量字段或超大字段，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

VendorProductAffected VersionsCPESubscribe
Kludexstarlette >= 0.4.1, < 1.3.1 -

II. Public POCs for CVE-2026-54283

#POC DescriptionSource LinkShenlong Link
AI-Generated POCVerified env Premium
Qwen3.6-35B-A3B · 9755 chars
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III. Intelligence Information for CVE-2026-54283

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Vendor Advisories for CVE-2026-54283 (1)

Same Patch Batch · Kludex · 2026-06-22 · 6 CVEs total

CVE-2026-535397.5 HIGHPython-Multipart: Quadratic-time querystring parsing with semicolon separators causes CPU
CVE-2026-535373.7 LOWPython-Multipart: Content-Disposition parameter smuggling via RFC 2231/5987 extended param
CVE-2026-535403.7 LOWPython-Multipart: Negative Content-Length in parse_form buffers the entire body in memory
CVE-2026-535383.7 LOWPython-Multipart: Semicolon treated as querystring field separator enables parameter smugg
CVE-2026-542823.7 LOWStarlette: Unvalidated request path concatenated into authority poisons request.url.hostna

IV. Related Vulnerabilities

Same product: starlette
Same vendor: Kludex
Same weakness: CWE-770

V. Comments for CVE-2026-54283

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