Contao up to 5.3.46/5.7.6 Crawler improper authorization

Summaryinfo

A vulnerability, which was classified as problematic, was found in Contao up to 5.3.46/5.7.6. The impacted element is an unknown function of the component Crawler. The manipulation results in improper authorization. This vulnerability was named CVE-2026-55824. The attack may be performed from remote. There is no available exploit.

Detailsinfo

A vulnerability classified as problematic has been found in Contao up to 5.3.46/5.7.6. Affected is some unknown functionality of the component Crawler. The manipulation with an unknown input leads to a improper authorization vulnerability. CWE is classifying the issue as CWE-285. The product does not perform or incorrectly performs an authorization check when an actor attempts to access a resource or perform an action. This is going to have an impact on confidentiality. CVE summarizes:

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.

The advisory is shared for download at github.com. This vulnerability is traded as CVE-2026-55824 since 06/17/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. There are neither technical details nor an exploit publicly available. The MITRE ATT&CK project declares the attack technique as T1548.002.

Upgrading to version 5.3.47 or 5.7.7 eliminates this vulnerability.

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Productinfo

Name

• Contao

Version

• 5.3.0
• 5.3.1
• 5.3.2
• 5.3.3
• 5.3.4
• 5.3.5
• 5.3.6
• 5.3.7
• 5.3.8
• 5.3.9
• 5.3.10
• 5.3.11
• 5.3.12
• 5.3.13
• 5.3.14
• 5.3.15
• 5.3.16
• 5.3.17
• 5.3.18
• 5.3.19
• 5.3.20
• 5.3.21
• 5.3.22
• 5.3.23
• 5.3.24
• 5.3.25
• 5.3.26
• 5.3.27
• 5.3.28
• 5.3.29
• 5.3.30
• 5.3.31
• 5.3.32
• 5.3.33
• 5.3.34
• 5.3.35
• 5.3.36
• 5.3.37
• 5.3.38
• 5.3.39
• 5.3.40
• 5.3.41
• 5.3.42
• 5.3.43
• 5.3.44
• 5.3.45
• 5.3.46
• 5.7.0
• 5.7.1
• 5.7.2
• 5.7.3
• 5.7.4
• 5.7.5
• 5.7.6

Website

• Product: https://github.com/contao/contao/

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