CVE-2026-40561 Affecting starlet package, versions <0.31-2+deb13u1
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-DEBIAN13-STARLET-16415145
- published4 May 2026
- disclosed3 May 2026
Introduced: 3 May 2026
CVE-2026-40561 (opens in a new tab)How to fix?
Upgrade Debian:13 starlet to version 0.31-2+deb13u1 or higher.
NVD Description
Note: Versions mentioned in the description apply only to the upstream starlet package and not the starlet package as distributed by Debian.
See How to fix? for Debian:13 relevant fixed versions and status.
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
- https://security-tracker.debian.org/tracker/CVE-2026-40561
- https://datatracker.ietf.org/doc/html/rfc7230#section-3.3.3
- https://github.com/kazuho/Starlet/commit/a7d5dfd1862aafa43e5eaca0fdb6acf4cc15b2d0.patch
- http://www.openwall.com/lists/oss-security/2026/05/03/1
- https://metacpan.org/release/KAZUHO/Starlet-0.32/changes