# CVE-2026-40561: Starlet versions through 0.31 for Perl allows HTTP Request Smuggling via Improper Header Precedence. Starlet…

Source: https://junglewise.ai/threats/cve-2026-40561-starlet-versions-through-0-31-for-perl-allows-http-request  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-05-03  
License: CC BY 4.0 with a link back

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.

Technologies: [Kazuho Starlet](https://junglewise.ai/threats/technologies/starlet). Vendors: [Kazuho](https://junglewise.ai/threats/vendors/kazuho).

## Quick answers

**Is CVE-2026-40561 exploited in the wild?** 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.

## Affected products

- Kazuho Starlet

## Related threats

- [Starlet memory exhaustion in chunked request decoding](https://junglewise.ai/threats/cve-2026-116128-starlet-versions-from-0-20-before-0-33-for-perl-allow-memory)
- [Starlet denial of service via large Content-Length](https://junglewise.ai/threats/cve-2026-115865-starlet-versions-before-0-33-for-perl-allow-a-request-declaring)