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CVE-2026-40561— Starlet versions through 0.31 for Perl allows HTTP Request Smuggling via Improper Header Precedence

Quick assessment

Affected
KAZUHO Starlet
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.

Starlet是Kazuho Oku个人开发者的一款高性能HTTP/1.1预分叉Web服务器。 Starlet 0.31及之前版本存在环境问题漏洞，该漏洞源于错误优先处理Content-Length标头而非Transfer-Encoding标头，可能导致HTTP请求夹带攻击。

AI Predicted 7.5 Difficulty: Moderate EPSS 0.36% · P30

Possible ATT&CK Techniques 1 AI

T1102 · Web Service

Affected Version Matrix 1

VendorProduct Version RangeStatus
KAZUHO Starlet ≤ 0.31 affected
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I. Basic Information for CVE-2026-40561

Vulnerability Information
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Vulnerability Title
Starlet versions through 0.31 for Perl allows HTTP Request Smuggling via Improper Header Precedence
Source: CVE Program / CVE List V5
Vulnerability Description
Starlet versions through 0.31 for Perl allows HTTP Request Smuggling via Improper Header Precedence. Starlet incorrectly prioritizes "Content-Length" over "Transfer-Encoding: chunked" when both headers are present in an HTTP request. Per RFC 7230 3.3.3, Transfer-Encoding must take precedence. An attacker could exploit this to smuggle malicious HTTP requests via a front-end reverse proxy.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
HTTP请求的解释不一致性(HTTP请求私运)
Source: CVE Program / CVE List V5
Vulnerability Title
Starlet 环境问题漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Starlet是Kazuho Oku个人开发者的一款高性能HTTP/1.1预分叉Web服务器。 Starlet 0.31及之前版本存在环境问题漏洞，该漏洞源于错误优先处理Content-Length标头而非Transfer-Encoding标头，可能导致HTTP请求夹带攻击。
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
KAZUHO Starlet 0 ~ 0.31 -

II. Public POCs for CVE-2026-40561

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III. Intelligence Information for CVE-2026-40561

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Patches & Fixes for CVE-2026-40561 (1)

Other References for CVE-2026-40561 (1)

IV. Related Vulnerabilities

Same weakness: CWE-444

V. Comments for CVE-2026-40561

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