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

{
  "id": "895e8894edf4321301511cceb017032a07d67682ae2f7bd356bb34280366b090",
  "url": "https://osv.dev/vulnerability/CVE-2026-40561",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Starlet versions through 0.31 for Perl allows HTTP Request Smuggling via Improper Header Precedence",
    "summary": "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.",
    "evidence": "osv:CVE-2026-40561",
    "products": [],
    "severity": "medium",
    "structured": {
      "id": "CVE-2026-40561",
      "aliases": [
        "CVE-2026-40561"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/kazuho/starlet",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "a7d5dfd1862aafa43e5eaca0fdb6acf4cc15b2d0"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "cpe": "cpe:2.3:a:kazuho:starlet:*:*:*:*:*:perl:*:*",
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "last_affected": "0.31"
                      }
                    ],
                    "source": "CPE_RANGE"
                  },
                  {
                    "range": [
                      {
                        "fixed": "a7d5dfd1862aafa43e5eaca0fdb6acf4cc15b2d0"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  }
                ]
              }
            }
          ],
          "versions": [
            "0.31",
            "0.30",
            "0.29",
            "0.28",
            "0.27_01",
            "0.26",
            "0.25",
            "0.24",
            "0.23",
            "0.22",
            "0.21",
            "0.20",
            "0.18",
            "0.17_01",
            "0.16",
            "0.15",
            "0.14",
            "0.13",
            "0.12",
            "0.11",
            "0.10",
            "0.08",
            "0.07",
            "0.05",
            "0.04",
            "0.01"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-40561.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:26.887659591Z",
      "provider": "osv",
      "references": [
        "https://cpan.org/modules",
        "https://datatracker.ietf.org/doc/html/rfc7230#section-3.3.3",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/40xxx/CVE-2026-40561.json",
        "https://metacpan.org/release/KAZUHO/Starlet-0.32/changes",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-40561",
        "https://github.com/kazuho/Starlet/commit/a7d5dfd1862aafa43e5eaca0fdb6acf4cc15b2d0.patch",
        "https://github.com/kazuho/Starlet"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-444"
        ],
        "cna_assigner": "CPANSec",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/40xxx/CVE-2026-40561.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-40561",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 493275,
  "published_at": "2026-05-03T00:57:31.519+00:00"
}