CVE-2026-40561: Kazuho Starlet

Medium severity, CVSS 5.3. EPSS: 0.4% chance of exploitation in the next 30 days.

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.

Affected products

• Kazuho Starlet: up to and including 0.31

Published 2026-05-03. Last modified 2026-06-17.