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CVE PROGRAM SOURCE RECORD5.3 Medium

CVE-2026-107843

Contao: The registration module re-sends activation mails on any unauthenticated POST, with no throttle and no captcha check

Description

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.

Affected products

Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.

contao contao

  • >= 4.1.0, < 5.3.50affected
  • >= 5.4.0-RC1, < 5.7.12affected

References