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.

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Advisories
Source ID Title
Github GHSA Github GHSA GHSA-mfxh-vp55-7gc6 Contao: The registration module re-sends activation mails
Fixes

Solution

No solution given by the vendor.


Workaround

No workaround given by the vendor.

History

Fri, 09 Oct 2026 20:45:00 +0000

Type Values Removed Values Added
First Time appeared Contao
Contao contao
Vendors & Products Contao
Contao contao

Fri, 09 Oct 2026 19:30:00 +0000

Type Values Removed Values Added
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.
Title Contao: The registration module re-sends activation mails on any unauthenticated POST, with no throttle and no captcha check
Weaknesses CWE-204
CWE-770
References
Metrics cvssV3_1

{'score': 5.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N'}


Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-10-09T19:21:32.011Z

Reserved: 2026-10-08T22:34:49.291Z

Link: CVE-2026-107843

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-10-09T20:17:10.167

Modified: 2026-10-09T20:17:10.167

Link: CVE-2026-107843

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-10-09T20:30:11Z

Weaknesses