@fastify/reply-from vulnerable to connection header abuse enabling stripping of proxy-added headers

{
  "id": "c1e76abbf913774f669a235bcc515798b8d4a195c596d23f7cfdcbe1cc8f25d3",
  "url": "https://osv.dev/vulnerability/CVE-2026-33805",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "@fastify/reply-from vulnerable to connection header abuse enabling stripping of proxy-added headers",
    "summary": "@fastify/reply-from v12.6.1 and earlier and @fastify/http-proxy v11.4.3 and earlier process the client's Connection header after the proxy has added its own headers via rewriteRequestHeaders. This allows attackers to retroactively strip proxy-added headers from upstream requests by listing them in the Connection header value. Any header added by the proxy for routing, access control, or security purposes can be selectively removed by a client. @fastify/http-proxy is also affected as it delegates to @fastify/reply-from. Upgrade to @fastify/reply-from v12.6.2 or @fastify/http-proxy v11.4.4 or later.",
    "evidence": "osv:CVE-2026-33805",
    "products": [],
    "severity": "critical",
    "structured": {
      "id": "CVE-2026-33805",
      "aliases": [
        "CVE-2026-33805",
        "GHSA-gwhp-pf74-vj37"
      ],
      "metrics": [
        {
          "type": "CVSS_V4",
          "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:L/SI:H/SA:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/fastify/fastify-http-proxy",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "15df3dc5eca55e2e61dba1745f422690b4a55257"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "cpe": "cpe:2.3:a:fastify:fastify\\/http-proxy:*:*:*:*:*:node.js:*:*",
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "11.4.4"
                      }
                    ],
                    "source": "CPE_RANGE"
                  }
                ]
              }
            },
            {
              "repo": "https://github.com/fastify/fastify-reply-from",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "457ac75f38bc846e8ab76a7cb1618d6c257b7fa2"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "12.6.2"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StandardRange"
                  },
                  {
                    "cpe": "cpe:2.3:a:fastify:reply-from:*:*:*:*:*:node.js:*:*",
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "12.6.2"
                      }
                    ],
                    "source": "CPE_RANGE"
                  }
                ]
              }
            }
          ],
          "versions": [
            "v11.4.3",
            "v11.4.2",
            "v11.4.1",
            "v11.4.0",
            "v11.3.0",
            "v11.2.0",
            "v11.1.1",
            "v11.1.0",
            "v11.0.1",
            "v11.0.0",
            "v10.0.2",
            "v10.0.1",
            "v10.0.0",
            "v9.5.0",
            "v9.4.0",
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            "v9.2.0",
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            "v8.4.0",
            "v8.3.0",
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            "v7.1.0",
            "v8.2.2",
            "v8.2.1",
            "v8.2.0",
            "v8.1.0",
            "v8.0.2",
            "v8.0.1",
            "v8.0.0",
            "v7.0.0",
            "v6.2.2",
            "v6.2.1",
            "v6.2.0",
            "v6.1.0",
            "v6.0.1",
            "v6.0.0",
            "v5.0.0",
            "v4.4.0",
            "v4.3.1",
            "v4.3.0",
            "v4.2.0",
            "v4.1.0",
            "v4.0.4",
            "v4.0.3",
            "v4.0.2",
            "v4.0.1",
            "v4.0.0",
            "v3.2.0",
            "v3.1.0",
            "v3.0.0",
            "v2.3.0",
            "v2.2.0",
            "v2.1.0",
            "v2.0.3",
            "v2.0.2",
            "v2.0.1",
            "v1.0.0",
            "v0.8.0",
            "v0.7.0",
            "v0.6.0",
            "v0.4.3",
            "v0.4.2",
            "v0.4.1",
            "v0.4.0",
            "v0.3.0",
            "v0.2.1",
            "v0.2.0",
            "v0.1.1",
            "v12.6.1",
            "v12.5.0",
            "v12.4.0",
            "v12.3.1",
            "v12.3.0",
            "v12.2.0",
            "v12.1.0",
            "v12.0.2",
            "v12.0.1",
            "v12.0.0",
            "v11.0.2",
            "v9.8.0",
            "v9.7.0",
            "v9.6.0",
            "v4.18.0",
            "v9.0.2",
            "v9.0.1",
            "v8.4.3",
            "v8.4.2",
            "v8.4.1",
            "v8.3.1",
            "v7.0.1",
            "v6.6.0",
            "v6.5.0",
            "v6.4.3",
            "v6.4.2",
            "v6.4.1",
            "v6.4.0",
            "v6.3.0",
            "v5.3.0",
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            "v5.0.2",
            "v5.0.1",
            "v3.5.0",
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            "v3.3.0",
            "v3.1.4",
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            "v3.1.1",
            "v2.0.0",
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            "v0.6.2",
            "v0.6.1",
            "v0.5.4",
            "v0.5.3",
            "v0.5.2",
            "v0.5.0",
            "v0.4.6",
            "v0.4.5",
            "v0.4.4",
            "v0.1.0"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-33805.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:42.443841538Z",
      "provider": "osv",
      "references": [
        "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33805.json",
        "https://access.redhat.com/errata/RHSA-2026:10175",
        "https://access.redhat.com/security/cve/CVE-2026-33805",
        "https://cna.openjsf.org/security-advisories.html",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33805.json",
        "https://github.com/fastify/fastify-reply-from/security/advisories/GHSA-gwhp-pf74-vj37",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-33805",
        "https://bugzilla.redhat.com/show_bug.cgi?id=2458651"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-644"
        ],
        "cna_assigner": "openjs",
        "unresolved_ranges": [
          {
            "extracted_events": [
              {
                "range": [
                  {
                    "fixed": "11.4.4"
                  }
                ],
                "source": "AFFECTED_FIELD",
                "strategy": "StandardRange"
              }
            ]
          }
        ],
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33805.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-33805",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 510185,
  "published_at": "2026-04-15T10:13:25.147+00:00"
}