CVE-2026-107843
mediumpriority · track · 0EPSS 0.003 · 19 %ileDEUSEPSS · scored 2026-10-27
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
Technical severity, 0–10. One row per scoring source.
base score 0–10 · higher = more severe · hover a vector to decode
ssvc
A stakeholder decision — act, attend, or track — from exploitation and impact.
weaknesses
The CWE weakness classes this flaw belongs to.
affected products (6)
Products and version ranges known to be affected.
advisories (2)
Vendor and ecosystem advisories describing this.
- WID-SEC-W-2026-2999Contao: Mehrere SchwachstellenDeutsch2026-08-24csaf · cert_bundDE
Ein Angreifer kann mehrere Schwachstellen in Contao ausnutzen, um Sicherheitsmaßnahmen zu umgehen, Berechtigungen zu erweitern und möglicherweise Administratorrechte zu erlangen, Cross-Site-Scripting-Angriffe durchzuführen, sensible Informationen offenzulegen und Daten zu manipulieren.
- GHSA-mfxh-vp55-7gc6Contao: The registration module re-sends activation mails2026-10-09ghsa · osvUS
`ModuleRegistration::compile()` reaches its follow-up registration branch on **any** POST to a page carrying the module. That branch checks neither `FORM_SUBMIT` nor the captcha result computed immediately above it, and `resendActivationMail()` leads to `OptInToken::send()`, which has no rate limit at all. ### Impact Anyone on the internet can make a Contao installation send unlimited mail to an address of their choosing, from the site's own sender and reputation, at one outbound message per HTTP request. That is both a nuisance for the recipient and a deliverability risk for the site operator. The same request is a reliable account oracle for "this address has a pending registration on this site", which is exactly the sort of membership fact a public site is usually expected not to disclose. **Honest bound.** The target must have an unconfirmed registration, that is `tl_member.disable = 1` together with an unconfirmed `reg-` opt-in token. An attacker can create that state for an arbitrary address, since registration requires no ownership proof, but on a site where `reg_activate` is off the branch is unreachable.
sources
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references (4) nvd
External citations — patches, advisories, analysis.
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