CVE-2026-40561: Starlet versions through 0.31 for Perl allows HTTP Request Smuggling via Improper Header Precedence. Starlet…
CVE-2026-40561 · Severity: medium · CVSS 5.3 · Published 2026-05-03
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.
No. Junglewise Threat Intelligence has no report of CVE-2026-40561 being exploited in the wild.
How severe is CVE-2026-40561?
Medium severity, with a CVSS score of 5.3, published 3 May 2026.
Which products and versions are affected?
Kazuho Starlet. The advisory does not name versions.
Is there a fix for CVE-2026-40561?
No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
Am I affected by CVE-2026-40561?
Check whether you run Kazuho Starlet. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.