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Guzzle: Noncanonical host can bypass host-based checks

Type: advisorySources: OSV

Guzzle is an extensible PHP HTTP client. Prior to 7.15.2 and 8.0.1, Guzzle gives a transport the request URI as text and supplies the Host header separately. The cURL handlers set CURLOPT_URL to the URI exactly as written and push that Host into CURLOPT_HTTPHEADER; StreamHandler does the same through fopen(). libcurl then parses the authority itself, percent-decoding it and, on an IDN-capable build, applying IDNA mapping, and uses the result to resolve, connect, name the TLS peer and address a proxy CONNECT, while the supplied Host suppresses the aligned one libcurl would have generated. For a URI host written as 127.0.0.%31, filter_var() rejects the host as an IP literal, yet libcurl decodes it to 127.0.0.1 and reaches loopback with no DNS lookup while the server receives Host: 127.0.0.%31. An attacker who influences a fetched URI can therefore reach a host the application's checks excluded and read whatever the host exposes of the response. The same divergence moves Guzzle's own decisions onto a spelling the transport does not use: no_proxy selects proxy routing from the literal host, and RedirectMiddleware decides from it whether to strip Authorization and Cookie. Exploitation requires the application to build a request URI from untrusted input and to make a host decision before handing it to Guzzle. This issue is fixed in versions 7.15.2 and 8.0.1.

Products
Not specified
Affected versions
Not specified
Fixed versions
Not specified
CVEs
CVE-2026-69246
Confirmed fixed CVEs
Not specified
Updated in this feed
3 Nov 2026, 09:54 UTC · Revision 1

Source evidence

Guzzle: Noncanonical host can bypass host-based checks

core-osv · Original source

Published 3 Aug 2026, 21:07 UTC

Guzzle is an extensible PHP HTTP client. Prior to 7.15.2 and 8.0.1, Guzzle gives a transport the request URI as text and supplies the Host header separately. The cURL handlers set CURLOPT_URL to the URI exactly as written and push that Host into CURLOPT_HTTPHEADER; StreamHandler does the same through fopen(). libcurl then parses the authority itself, percent-decoding it and, on an IDN-capable build, applying IDNA mapping, and uses the result to resolve, connect, name the TLS peer and address a proxy CONNECT, while the supplied Host suppresses the aligned one libcurl would have generated. For a URI host written as 127.0.0.%31, filter_var() rejects the host as an IP literal, yet libcurl decodes it to 127.0.0.1 and reaches loopback with no DNS lookup while the server receives Host: 127.0.0.%31. An attacker who influences a fetched URI can therefore reach a host the application's checks excluded and read whatever the host exposes of the response. The same divergence moves Guzzle's own decisions onto a spelling the transport does not use: no_proxy selects proxy routing from the literal host, and RedirectMiddleware decides from it whether to strip Authorization and Cookie. Exploitation requires the application to build a request URI from untrusted input and to make a host decision before handing it to Guzzle. This issue is fixed in versions 7.15.2 and 8.0.1.

osv:CVE-2026-69246
Complete source record
{
  "id": "10ebe7769f0d79bed5e10c22480c752505fe09bf1ed1d7523eb4b9d99a990e01",
  "url": "https://osv.dev/vulnerability/CVE-2026-69246",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Guzzle: Noncanonical host can bypass host-based checks",
    "summary": "Guzzle is an extensible PHP HTTP client. Prior to 7.15.2 and 8.0.1, Guzzle gives a transport the request URI as text and supplies the Host header separately. The cURL handlers set CURLOPT_URL to the URI exactly as written and push that Host into CURLOPT_HTTPHEADER; StreamHandler does the same through fopen(). libcurl then parses the authority itself, percent-decoding it and, on an IDN-capable build, applying IDNA mapping, and uses the result to resolve, connect, name the TLS peer and address a proxy CONNECT, while the supplied Host suppresses the aligned one libcurl would have generated. For a URI host written as 127.0.0.%31, filter_var() rejects the host as an IP literal, yet libcurl decodes it to 127.0.0.1 and reaches loopback with no DNS lookup while the server receives Host: 127.0.0.%31. An attacker who influences a fetched URI can therefore reach a host the application's checks excluded and read whatever the host exposes of the response. The same divergence moves Guzzle's own decisions onto a spelling the transport does not use: no_proxy selects proxy routing from the literal host, and RedirectMiddleware decides from it whether to strip Authorization and Cookie. Exploitation requires the application to build a request URI from untrusted input and to make a host decision before handing it to Guzzle. This issue is fixed in versions 7.15.2 and 8.0.1.",
    "evidence": "osv:CVE-2026-69246",
    "products": [],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-69246",
      "aliases": [
        "CVE-2026-69246",
        "GHSA-v5mv-p594-2x33"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/guzzle/guzzle",
              "type": "GIT",
              "events": [
                {
                  "introduced": "643356760d8efce521dfce2587d63fd9d0c70d72"
                },
                {
                  "fixed": "3aeea0406aab88cbbd86531313d7cebf8ae149a4"
                },
                {
                  "introduced": "0"
                },
                {
                  "fixed": "744101956d78b7c1384d0cbf379db13e859167bf"
                }
              ],
              "database_specific": {
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                  {
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                        "introduced": "8.0.0"
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                        "fixed": "8.0.1"
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                    "source": "AFFECTED_FIELD",
                    "strategy": "StringRangeExpression"
                  },
                  {
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "7.15.2"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StringRangeExpression"
                  },
                  {
                    "range": [
                      {
                        "fixed": "3aeea0406aab88cbbd86531313d7cebf8ae149a4"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  },
                  {
                    "range": [
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                        "fixed": "744101956d78b7c1384d0cbf379db13e859167bf"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  },
                  {
                    "range": [
                      {
                        "fixed": "744101956d78b7c1384d0cbf379db13e859167bf"
                      }
                    ],
                    "source": "REFERENCES_TAG",
                    "original_tag": "7.15.2"
                  },
                  {
                    "range": [
                      {
                        "fixed": "3aeea0406aab88cbbd86531313d7cebf8ae149a4"
                      }
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                    "source": "REFERENCES_TAG",
                    "original_tag": "8.0.1"
                  }
                ]
              }
            }
          ],
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          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-69246.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:27.960200993Z",
      "provider": "osv",
      "references": [
        "https://github.com/guzzle/guzzle/releases/tag/7.15.2",
        "https://github.com/guzzle/guzzle/releases/tag/8.0.1",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/69xxx/CVE-2026-69246.json",
        "https://github.com/guzzle/guzzle/security/advisories/GHSA-v5mv-p594-2x33",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-69246",
        "https://github.com/guzzle/guzzle/commit/3aeea0406aab88cbbd86531313d7cebf8ae149a4",
        "https://github.com/guzzle/guzzle/commit/744101956d78b7c1384d0cbf379db13e859167bf",
        "https://github.com/guzzle/guzzle/pull/3907",
        "https://github.com/guzzle/guzzle/pull/3908"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-180",
          "CWE-436",
          "CWE-918",
          "CWE-941"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/69xxx/CVE-2026-69246.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-69246",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 494339,
  "published_at": "2026-08-03T21:07:04.228+00:00"
}