CVE-2026-107843 Details
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.
A vulnerability in Contao's registration module allows an unauthenticated attacker to resend activation emails without restriction. This issue affects Contao versions 4.1.0 prior to 5.3.50 and 5.7.12. The vulnerability arises because the 'ModuleRegistration::compile()' method does not properly validate form submissions or captcha results, enabling repeated activation emails to be sent to addresses with pending registrations. The flaw can be exploited only when 'reg_activate' is enabled and the target has an unconfirmed registration and opt-in token.
Users can upgrade to Contao versions 5.3.50 or 5.7.12 to address this vulnerability.
Metrics
CVSS 4.0 Severity and Vector Strings:
VolerionCVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
Volerion
Assessed Oct 9, 2026CISA-ADP
Assessed Oct 13, 2026References to Advisories, Solutions, and Tools
By selecting these links, you will be leaving this site. These are references gathered from the official CVE record and are not endorsed by Volerion.
| URL | Source(s) | Tag(s) |
|---|---|---|
| https://github.com/contao/contao/commit/2ea6117f9049db7221679251cfc41e67d941a74b | [email protected] | Source CodeVendor |
| https://github.com/contao/contao/releases/tag/5.3.50 | [email protected] | Release NotesVendor |
| https://github.com/contao/contao/releases/tag/5.7.12 | [email protected] | Release NotesVendor |
| https://github.com/contao/contao/security/advisories/GHSA-mfxh-vp55-7gc6 | [email protected] | AdvisoryRemedyVendor |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-204 | Observable Response Discrepancy | [email protected] |
| CWE-770 | Allocation of Resources Without Limits or Throttling | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| Contao | >= 4.1.0, < 5.3.50 (semver) 5.7.12 (semver) |
CPE
Remediation
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Change History
2 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Oct 13, 2026 | CVE Modified | CISA-ADP |
| Oct 9, 2026 | New CVE Received | [email protected] |