fastify vulnerable to Body Schema Validation Bypass via Leading Space in Content-Type Header

{
  "id": "d4f87a8a8f48d8dd065b0428175e6d18768aa3fda136ec090f75456cdac77fc5",
  "url": "https://osv.dev/vulnerability/CVE-2026-33806",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "fastify vulnerable to Body Schema Validation Bypass via Leading Space in Content-Type Header",
    "summary": "Impact: Fastify applications using schema.body.content for per-content-type body validation can have validation bypassed entirely by prepending a space to the Content-Type header. The body is still parsed correctly but schema validation is skipped. This is a regression introduced in fastify >= 5.3.2 by the fix for CVE-2025-32442 Patches: Upgrade to fastify v5.8.5 or later. Workarounds: None. Upgrade to the patched version.",
    "evidence": "osv:CVE-2026-33806",
    "products": [],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-33806",
      "aliases": [
        "CVE-2025-32442",
        "CVE-2026-33806",
        "GHSA-247c-9743-5963",
        "GHSA-mg2h-6x62-wpwc"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/fastify/fastify",
              "type": "GIT",
              "events": [
                {
                  "introduced": "32f7e1eb97b638bad3ff8b80948e5b2c07d1b8b5"
                },
                {
                  "fixed": "3983cce8124714242099e8756a7a9a80a0ba0aea"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "5.3.2"
                      },
                      {
                        "fixed": "5.8.5"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StandardRange"
                  },
                  {
                    "cpe": "cpe:2.3:a:fastify:fastify:*:*:*:*:*:node.js:*:*",
                    "range": [
                      {
                        "introduced": "5.3.2"
                      },
                      {
                        "fixed": "5.8.5"
                      }
                    ],
                    "source": "CPE_RANGE"
                  }
                ]
              }
            }
          ],
          "versions": [
            "v5.8.4",
            "v5.8.3",
            "v5.8.2",
            "v5.8.1",
            "v5.8.0",
            "v5.7.4",
            "v5.7.3",
            "v5.7.2",
            "v5.7.1",
            "v5.7.0",
            "v5.6.2",
            "v5.6.1",
            "v5.6.0",
            "v5.5.0",
            "v5.4.0",
            "v5.3.3",
            "v5.3.2"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-33806.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:29.290849569Z",
      "provider": "osv",
      "references": [
        "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33806.json",
        "https://access.redhat.com/security/cve/CVE-2026-33806",
        "https://cna.openjsf.org/security-advisories.html",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33806.json",
        "https://github.com/fastify/fastify/security/advisories/GHSA-mg2h-6x62-wpwc",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-33806",
        "https://bugzilla.redhat.com/show_bug.cgi?id=2458596"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-1287"
        ],
        "cna_assigner": "openjs",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33806.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2025-32442",
        "evidence": "/aliases"
      },
      {
        "value": "CVE-2026-33806",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 496220,
  "published_at": "2026-04-15T00:14:02.376+00:00"
}