Vulnerability-Lookup

CVE-2026-69246 (GCVE-0-2026-69246)

Vulnerability from cvelistv5 – Published: 2026-08-03 21:07 – Updated: 2026-08-04 14:06

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.

Severity

7.2 (High)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N

SSVC

Exploitation: none Automatable: yes Technical Impact: partial

CISA Coordinator (v2.0.3)

CWE

CWE-180 - Incorrect Behavior Order: Validate Before Canonicalize
CWE-436 - Interpretation Conflict
CWE-918 - Server-Side Request Forgery (SSRF)
CWE-941 - Incorrectly Specified Destination in a Communication Channel

Assigner

GitHub_M

References

7 references

URL	Tags
https://github.com/guzzle/guzzle/security/advisor…	x_refsource_CONFIRM
https://github.com/guzzle/guzzle/pull/3907	x_refsource_MISC
https://github.com/guzzle/guzzle/pull/3908	x_refsource_MISC
https://github.com/guzzle/guzzle/commit/3aeea0406…	x_refsource_MISC
https://github.com/guzzle/guzzle/commit/744101956…	x_refsource_MISC
https://github.com/guzzle/guzzle/releases/tag/7.15.2	x_refsource_MISC
https://github.com/guzzle/guzzle/releases/tag/8.0.1	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
guzzle	guzzle	Affected: >= 8.0.0, < 8.0.1 Affected: < 7.15.2

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GHSA-V5MV-P594-2X33

Vulnerability from github – Published: 2026-08-03 21:07 – Updated: 2026-08-03 21:07

Summary

Guzzle: Noncanonical host can bypass host-based checks

Details

Impact

In affected versions, 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 it would have generated. In http://127.0.0.%31/ the URI host is one filter_var() rejects 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 it 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. The cookie middleware extracts Set-Cookie against the URI Guzzle produced, not the authority contacted, so for a raw divergent URI the cookie is stored under the URI host as written. Where Guzzle rewrote that URI but left a divergent Host, or where the caller supplied one, the cookie is stored under the canonical name and replayed by ordinary later requests to it. With a third-party UriInterface, a host of blocked.example.com@127.0.0.1 reaches 127.0.0.1 through all three handlers and generates Authorization: Basic from userinfo the application never wrote.

Exploitation requires the application to build a request URI from untrusted input and to make a host decision before handing it to Guzzle. Applications that only fetch URIs they construct themselves are not affected, and an exact allowlist of canonical names ordinarily fails closed; the exposure is to denylists, private-range and IP-literal checks, and any check that treats an unresolvable name as safe. The raw Unicode class needs an IDNA transformation somewhere: either a libcurl built with IDN support or Guzzle's own idn_conversion, off by default on both branches, which rewrites the URI in Client::buildUri() before a handler sees it and leaves a prebuilt request's explicit Host as written, while a request the client builds derives that header from the rewritten URI and produces no divergence. Noncanonical numeric spellings such as 127.1, 2130706433, 0x7f000001 and 0177.0.0.1 remain accepted after the patch and reach whatever the transport reads them as, loopback or a routable public host, and the cURL and stream handlers can differ, so a check comparing a host against an address as text stays bypassable. Guzzle does not offer SSRF protection, and neither cache poisoning nor cross-tenant compromise was established.

Patches

This is a summary; the patches are the authority. The issue is fixed in 7.15.2 and 8.0.1, which validate the request host in all three built-in handlers before any network I/O. A URI host is rejected for a byte outside 0x21 to 0x7E, a percent escape, a URI authority delimiter, unbalanced brackets, or numeric-looking parts followed by a trailing dot. That last rule is deliberately conservative and also refuses out-of-range forms libcurl keeps as names, such as 256.0.0.1.. An explicit Host header must be printable ASCII, and on 7.15.2 free of percent escapes. The client also regenerates a derived Host when it rewrites the request URI. Versions before 7.15.2 and version 8.0.0 are affected.

Workarounds

If you cannot upgrade, constrain the host yourself before handing a URI to Guzzle, and constrain any explicit Host header separately, on every redirect hop. The URI rule assumes $uri is a validated GuzzleHttp\Psr7\Uri, so re-parse a third-party UriInterface with new Uri((string) $uri) first.

$host = $uri->getHost();

if (
    preg_match('/\A[\x21-\x7E]*\z/D', $host) !== 1
    || strpbrk($host, '%@/?#\\') !== false
    || substr($host, -1) === '.'
) {
    throw new RuntimeException('Refusing to fetch this URI host.');
}

if (
    preg_match('/\A[\x21-\x7E]*\z/D', $hostHeader) !== 1
    || strpos($hostHeader, '%') !== false
) {
    throw new RuntimeException('Refusing to send this Host header.');
}

It differs from the patch in both directions: it refuses example.com., which the patch accepts, and it does not canonicalize 127.1 or 0x7f000001. Reparsing the URI separates a valid port from the host and rejects malformed bracket forms, so the snippet checks the host component alone. idn_conversion => true is not an access control, since IDNA maps １２７。０。０。１ onto 127.0.0.1 and direct handler use bypasses it, and Uri::getHost() is not an SSRF boundary: it is the host as written, not the host a transport connects to. Where the destination matters, resolve the host and check the addresses, and use a separate cookie jar for untrusted origins.

Severity

7.2 (High)


                  
                    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N

Show details on source website

JSON

To clipboard

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        "name": "guzzlehttp/guzzle"
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      ]
    }
  ],
  "aliases": [
    "CVE-2026-69246"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-180",
      "CWE-436",
      "CWE-918",
      "CWE-941"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-08-03T21:07:26Z",
    "nvd_published_at": null,
    "severity": "HIGH"
  },
  "details": "### Impact\n\nIn affected versions, 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 it would have generated. In `http://127.0.0.%31/` the URI host is one `filter_var()` rejects 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`.\n\nAn attacker who influences a fetched URI can therefore reach a host the application\u0027s checks excluded and read whatever it exposes of the response. The same divergence moves Guzzle\u0027s 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`. The cookie middleware extracts `Set-Cookie` against the URI Guzzle produced, not the authority contacted, so for a raw divergent URI the cookie is stored under the URI host as written. Where Guzzle rewrote that URI but left a divergent `Host`, or where the caller supplied one, the cookie is stored under the canonical name and replayed by ordinary later requests to it. With a third-party `UriInterface`, a host of `blocked.example.com@127.0.0.1` reaches `127.0.0.1` through all three handlers and generates `Authorization: Basic` from userinfo the application never wrote.\n\nExploitation requires the application to build a request URI from untrusted input and to make a host decision before handing it to Guzzle. Applications that only fetch URIs they construct themselves are not affected, and an exact allowlist of canonical names ordinarily fails closed; the exposure is to denylists, private-range and IP-literal checks, and any check that treats an unresolvable name as safe. The raw Unicode class needs an IDNA transformation somewhere: either a libcurl built with IDN support or Guzzle\u0027s own `idn_conversion`, off by default on both branches, which rewrites the URI in `Client::buildUri()` before a handler sees it and leaves a prebuilt request\u0027s explicit `Host` as written, while a request the client builds derives that header from the rewritten URI and produces no divergence. Noncanonical numeric spellings such as `127.1`, `2130706433`, `0x7f000001` and `0177.0.0.1` remain accepted after the patch and reach whatever the transport reads them as, loopback or a routable public host, and the cURL and stream handlers can differ, so a check comparing a host against an address as text stays bypassable. Guzzle does not offer SSRF protection, and neither cache poisoning nor cross-tenant compromise was established.\n\n### Patches\n\nThis is a summary; the patches are the authority. The issue is fixed in `7.15.2` and `8.0.1`, which validate the request host in all three built-in handlers before any network I/O. A URI host is rejected for a byte outside `0x21` to `0x7E`, a percent escape, a URI authority delimiter, unbalanced brackets, or numeric-looking parts followed by a trailing dot. That last rule is deliberately conservative and also refuses out-of-range forms libcurl keeps as names, such as `256.0.0.1.`. An explicit `Host` header must be printable ASCII, and on `7.15.2` free of percent escapes. The client also regenerates a derived `Host` when it rewrites the request URI. Versions before `7.15.2` and version `8.0.0` are affected.\n\n### Workarounds\n\nIf you cannot upgrade, constrain the host yourself before handing a URI to Guzzle, and constrain any explicit `Host` header separately, on every redirect hop. The URI rule assumes `$uri` is a validated `GuzzleHttp\\Psr7\\Uri`, so re-parse a third-party `UriInterface` with `new Uri((string) $uri)` first.\n\n```php\n$host = $uri-\u003egetHost();\n\nif (\n    preg_match(\u0027/\\A[\\x21-\\x7E]*\\z/D\u0027, $host) !== 1\n    || strpbrk($host, \u0027%@/?#\\\\\u0027) !== false\n    || substr($host, -1) === \u0027.\u0027\n) {\n    throw new RuntimeException(\u0027Refusing to fetch this URI host.\u0027);\n}\n\nif (\n    preg_match(\u0027/\\A[\\x21-\\x7E]*\\z/D\u0027, $hostHeader) !== 1\n    || strpos($hostHeader, \u0027%\u0027) !== false\n) {\n    throw new RuntimeException(\u0027Refusing to send this Host header.\u0027);\n}\n```\n\nIt differs from the patch in both directions: it refuses `example.com.`, which the patch accepts, and it does not canonicalize `127.1` or `0x7f000001`. Reparsing the URI separates a valid port from the host and rejects malformed bracket forms, so the snippet checks the host component alone. `idn_conversion =\u003e true` is not an access control, since IDNA maps `\uff11\uff12\uff17\u3002\uff10\u3002\uff10\u3002\uff11` onto `127.0.0.1` and direct handler use bypasses it, and `Uri::getHost()` is not an SSRF boundary: it is the host as written, not the host a transport connects to. Where the destination matters, resolve the host and check the addresses, and use a separate cookie jar for untrusted origins.",
  "id": "GHSA-v5mv-p594-2x33",
  "modified": "2026-08-03T21:07:26Z",
  "published": "2026-08-03T21:07:26Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/guzzle/guzzle/security/advisories/GHSA-v5mv-p594-2x33"
    },
    {
      "type": "WEB",
      "url": "https://github.com/guzzle/guzzle/pull/3907"
    },
    {
      "type": "WEB",
      "url": "https://github.com/guzzle/guzzle/pull/3908"
    },
    {
      "type": "WEB",
      "url": "https://github.com/guzzle/guzzle/commit/3aeea0406aab88cbbd86531313d7cebf8ae149a4"
    },
    {
      "type": "WEB",
      "url": "https://github.com/guzzle/guzzle/commit/744101956d78b7c1384d0cbf379db13e859167bf"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/guzzle/guzzle"
    },
    {
      "type": "WEB",
      "url": "https://github.com/guzzle/guzzle/releases/tag/7.15.2"
    },
    {
      "type": "WEB",
      "url": "https://github.com/guzzle/guzzle/releases/tag/8.0.1"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Guzzle: Noncanonical host can bypass host-based checks"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.

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