CVE-2026-107843

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.

CVSS 3.1

5.3CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

EPSS

0.3% chance of exploitation in the next 30 days; higher than 19% of CVEs (scores of 2026-10-25)

CWEs

CWE-204, CWE-770

Published

2026-10-09

Modified

2026-10-16

Record from

the NVD, synced 2026-10-19

References

• https://github.com/contao/contao/commit/2ea6117f9049db7221679251cfc41e67d941a74b
• https://github.com/contao/contao/releases/tag/5.3.50
• https://github.com/contao/contao/releases/tag/5.7.12
• https://github.com/contao/contao/security/advisories/GHSA-mfxh-vp55-7gc6

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