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No exploitation reportedFix available

CVE-2026-40561

No exploitation reported by the sources we read.

  • Published2026-05-03
  • WeaknessCWE-444

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

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.

Timeline

dates in UTC
  1. 2026-05-0301:15CVE publishedNVD

Versions per branch

NVD
Kazuho starlet
BranchAffectedFixed in
0.31≤ 0.31no fix published

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Products declared by the CNA1 product

As CPANSec, the CNA that assigned this CVE, declared them in the CVE record; versions as written.

Source: the CNA record (CVE Program), © The MITRE Corporation,CVE Terms of UseCVE recordupdated 2026-05-07

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

  • perl-starletAlpine:v3.24all versions · fixed in 0.32-r0
  • perl-starletAlpine:v3.23all versions · fixed in 0.32-r0
  • perl-StarletMageia:9all versions · fixed in 0.310.0-4.1.mga9
  • starletUbuntu:26.10all versions · no fixed version listed
  • starletUbuntu:26.04:LTSall versions · no fixed version listed
  • starletUbuntu:25.10all versions · no fixed version listed
  • starletUbuntu:24.04:LTSall versions · no fixed version listed
  • starletUbuntu:22.04:LTSall versions · no fixed version listed

6 more package ranges on OSV.dev

Full record on NVD

Fix

Advisories and patches

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof of concept
Metasploit modules
none listed
Metasploit Framework

Sources

Identifiers

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
Published
2026-05-03
Last Modified
2026-10-26
NVD status
Modified
GitHub Advisory
GHSA-2xqx-75wg-w86v

Frequently asked questions

What is 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.

Is CVE-2026-40561 actively exploited?

Active exploitation of CVE-2026-40561 has not been confirmed. Its EPSS score was 0.4% on 2026-11-05, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2026-40561?

CVE-2026-40561 has a CVSS v3 base score of 5.3 (MEDIUM severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N.

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