CVE-2026-40561

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 3.1

5.3CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

EPSS

0.4% chance of exploitation in the next 30 days; higher than 29% of CVEs (scores of 2026-10-26)

CWE

CWE-444

Published

2026-05-03

Modified

2026-10-26

Record from

the NVD, synced 2026-10-26

Affected

• kazuho:starlet

References

• https://datatracker.ietf.org/doc/html/rfc7230#section-3.3.3
• https://github.com/kazuho/Starlet/commit/a7d5dfd1862aafa43e5eaca0fdb6acf4cc15b2d0.patch
• https://metacpan.org/release/KAZUHO/Starlet-0.32/changes
• http://www.openwall.com/lists/oss-security/2026/05/03/1

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