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CVE-2026-40561                                       CPAN Security Group
========================================================================

         CVE ID:  CVE-2026-40561
   Distribution:  Starlet
       Versions:  through 0.31

       MetaCPAN:  https://metacpan.org/dist/Starlet
       VCS Repo:  https://github.com/kazuho/Starlet

Starlet versions through 0.31 for Perl allows HTTP Request Smuggling
via Improper Header Precedence

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.

Problem types
-------------
- CWE-444 Inconsistent Interpretation of HTTP Requests ('HTTP
   Request/Response Smuggling')

Workarounds
-----------
Migrate to Starman 0.4018 or later which has fixed this issue or apply
the patch.

References
----------
https://datatracker.ietf.org/doc/html/rfc7230#section-3.3.3
https://github.com/kazuho/Starlet/commit/a7d5dfd1862aafa43e5eaca0fdb6acf4cc15b2d0.patch

Timeline
--------
- 2026-04-12: Issue identified
- 2026-04-28: Maintainer notified
- 2026-05-02: Determined that the issue was already public on GitHub

Credits
-------
CPANSec, finder