CVE-2026-55824: Contao/contao Contao Crawler Leaks Auth Credentials Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-3mr9-p497-58f6",
  "modified" : "2026-08-06T19:43:02Z",
  "published" : "2026-08-06T19:43:02Z",
  "aliases" : [ "CVE-2026-55824" ],
  "summary" : "Contao crawler leaks auth credentials to external hosts",
  "details" : "### Summary\nContao's crawler tries to prevent confidential HTTP client options from being sent to external domains by creating a scoped client: full options for root page origins, cleaned options for everything else. The cleaner removes `Cookie` and `Authorization` headers, but it removes the non-Symfony option names `basic_auth` and `bearer_auth` instead of Symfony HttpClient's real `auth_basic` and `auth_bearer` options.\n\nWhen `contao.crawl.default_http_client_options` contains Basic or Bearer authentication for a protected staging/production site, those credentials remain in the \"clean\" client used for external links or configured additional URIs. An attacker who can get an external URL crawled, for example through a link on a crawled page while the broken-link checker is enabled, can receive the crawler credentials.\n\n## Technical Detail\n\n### Root Cause\n\n```php\n// core-bundle/src/Crawl/Escargot/Factory.php:175-209 @ e550b92a01ef625bd546e6c3956dd200af05ebf0\nprivate function createHttpClient(array $options = []): HttpClientInterface\n{\n    $options = array_merge_recursive(\n        [\n            'headers' => [\n                'accept' => 'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8',\n                'user-agent' => self::USER_AGENT,\n            ],\n            'max_duration' => 10,\n        ],\n        array_merge_recursive($this->getDefaultHttpClientOptions(), $options),\n    );\n\n    $cleanOptions = $this->cleanOptionsFromConfidentialData($options);\n\n    if ($options === $cleanOptions) {\n        return ($this->httpClientFactory)($options);\n    }\n\n    $scopedOptionsByRegex = [];\n\n    foreach ($this->getRootPageUriCollection()->all() as $rootPageUri) {\n        $scopedOptionsByRegex[preg_quote($this->getOriginFromUri($rootPageUri))] = $options;\n    }\n\n    return new ScopingHttpClient(($this->httpClientFactory)($cleanOptions), $scopedOptionsByRegex);\n}\n```\n\n```php\n// core-bundle/src/Crawl/Escargot/Factory.php:226-247 @ e550b92a01ef625bd546e6c3956dd200af05ebf0\nforeach ($options as $k => $v) {\n    if ('headers' === $k) {\n        foreach ($v as $header => $value) {\n            if (\\in_array(strtolower($header), ['authorization', 'cookie'], true)) {\n                continue;\n            }\n\n            $cleanOptions['headers'][$header] = $value;\n        }\n\n        continue;\n    }\n\n    if ('basic_auth' === $k || 'bearer_auth' === $k) {\n        continue;\n    }\n\n    $cleanOptions[$k] = $v;\n}\n```\n\nSymfony HttpClient authentication options are `auth_basic` and `auth_bearer`; Contao's own manual documents `auth_basic` for crawler Basic Authentication. Because the cleaner only strips `basic_auth` and `bearer_auth`, the \"clean\" default client for non-root-page hosts still carries the real auth options. The existing factory test intends to assert that `Authorization` is not sent to `www.foreign-domain.com`, but its mock client factory ignores the `$defaultOptions` argument, so it does not catch auth options that survive into `HttpClient::create($cleanOptions)`.\n\n\n## Suggested Mitigation\n\nStrip the actual Symfony HttpClient authentication option keys from the clean client. Include NTLM as a defensive extension because Symfony documents it as another auth option.\n\n```diff\n-            if ('basic_auth' === $k || 'bearer_auth' === $k) {\n+            if (\\in_array($k, ['auth_basic', 'auth_bearer', 'auth_ntlm', 'basic_auth', 'bearer_auth'], true)) {\n                 continue;\n             }\n```\n\nAlso update the factory test so the mock factory records or preserves `$defaultOptions`; otherwise the test does not verify what `HttpClient::create($cleanOptions)` receives in production.\n\n## Impact\n\n- **Direct primitive**: disclosure of crawler Basic/Bearer credentials to an external host reached by the crawler.\n- **Chain potential**: if those credentials protect a staging or pre-publication environment, an attacker can use them to access that environment. The impact depends on what the leaked credential unlocks.\n- **Realistic exploitation**: a content editor adds a link to `https://attacker.example/probe` on a page that the crawler visits. When an administrator or scheduled maintenance run starts the broken-link checker with crawler Basic/Bearer authentication configured, the request to the attacker URL includes the generated `Authorization` header.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:L/I:N/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "contao/contao"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "4.13.0"
      }, {
        "fixed" : "5.3.47"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "contao/contao"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "5.4.0"
      }, {
        "fixed" : "5.7.7"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "contao/core-bundle"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "4.13.0"
      }, {
        "fixed" : "5.3.47"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "contao/core-bundle"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "5.4.0"
      }, {
        "fixed" : "5.7.7"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/contao/contao/security/advisories/GHSA-3mr9-p497-58f6"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-55824"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/contao/contao/commit/5bc6e3f900c439313df57aa561d0865792aafa05"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/contao/contao/commit/80425d28cdf66280a209bd3f5bc31b1a76901a04"
  }, {
    "type" : "WEB",
    "url" : "https://contao.org/en/security-advisories/credentials-disclosure-in-the-crawler"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/FriendsOfPHP/security-advisories/blob/master/contao/contao/CVE-2026-55824.yaml"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/FriendsOfPHP/security-advisories/blob/master/contao/core-bundle/CVE-2026-55824.yaml"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/contao/contao"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-200" ],
    "severity" : "LOW",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-08-06T19:43:02Z",
    "nvd_published_at" : "2026-07-31T19:17:11Z"
  }
}