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.
CVSS Score
MEDIUM
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Kazuho | Starlet | <= 0.31 |
Related Weaknesses (CWE)
References
- https://datatracker.ietf.org/doc/html/rfc7230#section-3.3.3Third Party Advisory
- https://github.com/kazuho/Starlet/commit/a7d5dfd1862aafa43e5eaca0fdb6acf4cc15b2dPatch
- https://metacpan.org/release/KAZUHO/Starlet-0.32/changes
- http://www.openwall.com/lists/oss-security/2026/05/03/1Mailing ListThird Party Advisory
FAQ
What is CVE-2026-40561?
CVE-2026-40561 is a vulnerability with a CVSS score of 5.3 (MEDIUM). 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 heade...
How severe is CVE-2026-40561?
CVE-2026-40561 has been rated MEDIUM with a CVSS base score of 5.3/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-40561?
Check the references section above for vendor advisories and patch information. Affected products include: Kazuho Starlet.