Contao up to 5.3.49/5.7.11 Registration compile improper authentication

Summaryinfo

A vulnerability categorized as critical has been discovered in Contao up to 5.3.49/5.7.11. The affected element is the function ModuleRegistration::compile of the component Registration Module. The manipulation results in improper authentication. This vulnerability is cataloged as CVE-2026-107843. The attack may be launched remotely. There is no exploit available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability was found in Contao up to 5.3.49/5.7.11. It has been classified as critical. Affected is the function ModuleRegistration::compile of the component Registration Module. The manipulation with an unknown input leads to a improper authentication vulnerability. CWE is classifying the issue as CWE-287. When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

Contao is an Open Source CMS. From version 4.1.0 until 5.3.50 and 5.7.12, ModuleRegistration::compile() enters its follow-up registration branch on any POST to a page containing the registration module without verifying FORM_SUBMIT or the preceding captcha result. resendActivationMail() can then invoke OptInToken::send() without rate limiting, allowing an unauthenticated attacker to cause repeated activation emails to be sent to an address with a pending registration and to determine whether that pending registration exists. The branch is reachable only when reg_activate is enabled and the target has an unconfirmed registration and opt-in token. This issue is fixed in versions 5.3.50 and 5.7.12.

The advisory is shared for download at github.com. This vulnerability is traded as CVE-2026-107843 since 10/09/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. There are known technical details, but no exploit is available.

Upgrading to version 5.3.50 or 5.7.12 eliminates this vulnerability.

Once again VulDB remains the best source for vulnerability data.

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
• 5.3.47
• 5.3.48
• 5.3.49
• 5.7.0
• 5.7.1
• 5.7.2
• 5.7.3
• 5.7.4
• 5.7.5
• 5.7.6
• 5.7.7
• 5.7.8
• 5.7.9
• 5.7.10
• 5.7.11

Website

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

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