What’s Vulnerable › Vulnerabilities

CVE-2026-40560: Starman versions before 0.4018 for Perl allows HTTP Request Smuggling via Improper Header Precedence

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-04-29 · updated 2026-07-24
• Weakness: CWE-444

Description

Starman versions before 0.4018 for Perl allows HTTP Request Smuggling via Improper Header Precedence. Starman 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.

Affected products

• MIYAGAWA Starman: before 0.4018 — fixed in 0.4018

How to fix

Upgrade to a fixed version: MIYAGAWA Starman 0.4018. Check the vendor advisory for mitigations.

References

• https://datatracker.ietf.org/doc/html/rfc7230#section-3.3.3
• https://github.com/miyagawa/Starman/commit/ced205f0805027e9d9c0731f8c40b104220604ed.patch
• https://metacpan.org/release/MIYAGAWA/Starman-0.4018/changes
• http://www.openwall.com/lists/oss-security/2026/04/29/1

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