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

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Summary

CVECVE-2026-40561
StatePUBLISHED
AssignerCPANSec
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-05-03 01:15:58 UTC
Updated2026-05-07 17:15:58 UTC
DescriptionStarlet 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.

Risk And Classification

Primary CVSS: v3.1 5.3 MEDIUM from ADP

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

EPSS: 0.000120000 probability, percentile 0.018350000 (date 2026-05-12)

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

VersionSourceTypeScoreSeverityVector
3.1ADPDECLARED5.3MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
3.1134c704f-9b21-4f2e-91b3-4a467353bcc0Secondary5.3MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
None

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

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Application Kazuho Starlet All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA KAZUHO Starlet affected 0.31 custom Not specified

References

ReferenceSourceLinkTags
datatracker.ietf.org/doc/html/rfc7230 9b29abf9-4ab0-4765-b253-1875cd9b441e datatracker.ietf.org Third Party Advisory
metacpan.org/release/KAZUHO/Starlet-0.32/changes 9b29abf9-4ab0-4765-b253-1875cd9b441e metacpan.org
github.com/kazuho/Starlet/commit/a7d5dfd1862aafa43e5eaca0fdb6acf4cc15b2d... 9b29abf9-4ab0-4765-b253-1875cd9b441e github.com Patch
www.openwall.com/lists/oss-security/2026/05/03/1 af854a3a-2127-422b-91ae-364da2661108 www.openwall.com Mailing List, Third Party Advisory
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: CPANSec (en)

Additional Advisory Data

SourceTimeEvent
CNA2019-11-19T00:00:00.000ZPatch submitted to Starlet 0.31
CNA2026-04-12T00:00:00.000ZIssue identified by CPANSec
CNA2026-04-28T00:00:00.000ZMaintainer notified
CNA2026-05-02T00:00:00.000ZDetermined that the issue was already public on GitHub
CNA2026-05-06T00:00:00.000ZStarlet 0.32 released with a fix

Solutions

CNA: Upgrade to Starlet 0.32 or later.

Workarounds

CNA: Migrate to Starman 0.4018 or later which has fixed this issue or apply the patch.

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