CVE-2026-40561

MEDIUM 5.3CVE-2026-40561 · Published 03/05/2026 · updated 26/10/2026

In short

CVE-2026-40561 is a MEDIUM (CVSS 5.3) vulnerability affecting starlet (kazuho).
Chance of exploitation in the next 30 days (EPSS): 0.36%, higher than 30.4% of all vulnerabilities.
No patched version is listed yet: follow the vendor's advisory in References.

Package	Affected versions	Patched versions
starlet kazuho	`≤ 0.31`	No fix yet

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.

References

datatracker.ietf.org/doc/html/rfc7230 · Third Party Advisory
kazuho/Starlet commit a7d5dfd · Patch
metacpan.org/release/KAZUHO/Starlet-0.32/changes
openwall.com/lists/oss-security/2026/05/03/1 · Mailing List

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