Contao crawler leaks auth credentials to external hosts

Summary

Contao is an Open Source CMS. In versions 4.13.40 through 5.3.46 and 5.7.0-RC1 through 5.7.6, the crawler leaks auth credentials to external hosts. Contao'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. When 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. This issue has been fixed in versions 5.3.47 and 5.7.7.

Timeline

1. Jul 31, 2026, 7:04 PM UTCCVE published
2. Jul 31, 2026, 7:58 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: no · Technical impact: partial

3. Jul 31, 2026, 7:58 PM UTCRecord last updated

Affected versions

• contao contao

  From 4.13.40 · fixed in 5.3.47; From 5.7.0-RC1 · fixed in 5.7.7

• contao/contaoPackagist

  From 4.13.0 · fixed in 5.3.47

• contao/contaoPackagist

  From 5.4.0 · fixed in 5.7.7

• contao/core-bundlePackagist

  From 4.13.0 · fixed in 5.3.47

• contao/core-bundlePackagist

  From 5.4.0 · fixed in 5.7.7

References 1