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Medium

Contao: Registration module re-sends activation emails

  • Disclosed: 09.10.2026
  • Updated: 11.10.2026 10:31

ModuleRegistration::compile() reaches its follow-up registration branch on any POST request 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 emails to an address of their choosing, sent from the site's own sender and reputation at a rate of 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 acts as a reliable account oracle indicating "this address has a pending registration on this site", which is membership information a public site is usually expected not to disclose.

Honest bound. The target must have an unconfirmed registration: specifically 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 proof of ownership; however, on a site where reg_activate is turned off, this branch is unreachable.

What to do

Update contao/core-bundle to version 5.3.50, 5.7.12, or later.

Affected software

Click a technology to see all vulnerabilities affecting it.

PlatformPackageVulnerable versionsFixed in
Composer package contao/core-bundle >= 4.1.0, < 5.3.50, >= 5.4.0-RC1, < 5.7.12 5.3.50, 5.7.12

References

CVSS score 5.3/10
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Weakness (CWE)
CWE-204, CWE-770
Platform
Composer
Package
contao/core-bundle
Disclosed
09.10.2026
Updated
11.10.2026 10:31

Sources and licenses · Edited or translated by DockRay; source rights and applicable licenses are retained.

OSV / GitHub Advisory Database - GHSA-mfxh-vp55-7gc6 - CC BY 4.0

Vulnerability history: contao/core-bundle

All published vulnerabilities of this package (Composer package), newest first. Shows whether this is a one-off slip or a package that needs watching.

All (40) in the archive
Total entries
40
First → latest
12.2019 10.2026
Without a fix
0
Exploited in attacks
0

Severity breakdown

  • Critical 4
  • High 7
  • Medium 23
  • Low 6

Disclosures per year

Severity:
  1. Contao: Registration module re-sends activation emails this entry
    Medium · 5.3 CVE-2026-107843 >= 4.1.0, < 5.3.50, >= 5.4.0-RC1, < 5.7.12 5.3.50, 5.7.12
  2. Contao affected by remote command execution through file upload
    High · 8.3 CVE-2024-45398 >= 4.0.0, < 4.13.49, >= 5.0.0, < 5.3.15, >= 5.4.0, < 5.4.3 4.13.49, 5.3.15, 5.4.3
  3. Contao: Possible cookie sharing with external domains while checking protected pages for broken links
    High · 8.3 CVE-2024-28235 >= 4.9.0, < 4.13.40, >= 5.0.0-RC1, < 5.3.4 4.13.40, 5.3.4
  4. Contao SQL injection in the file manager
    Critical · 9.8 CVE-2019-11512 >= 4.1.0, < 4.4.39, >= 4.5.0, < 4.7.5 4.4.39, 4.7.5
  5. Contao SQL injection in the backend and listing module
    Critical · 9.8 CVE-2017-16558 >= 4.0.0, < 4.4.8, >= 3.0.0, <= 3.5.30 4.4.8
  6. Cross site scripting via canonical tag in Contao
    High · 7.2 CVE-2022-24899 >= 4.13.0, < 4.13.3 4.13.3
  7. Contao CSRF Token Bypass
    High · 8.8 CVE-2019-10642 >= 4.7.0, < 4.7.3 4.7.3
  8. Contao Does Not Invalidate Existing Sessions When Password Changes
    Critical · 9.8 CVE-2019-10641 >= 4.0.0, < 4.4.37, >= 4.5.0, < 4.7.3 4.4.37, 4.7.3
  9. Contao Core directory traversal vulnerability
    High · 8.8 CVE-2017-10993 >= 4.0.0, < 4.4.1 4.4.1
  10. Contao Does Not Expire Tokens Correctly
    Critical · 9.8 CVE-2019-10643 >= 4.7.0, < 4.7.3 4.7.3
  11. Privilege escalation via form generator
    High · 8.0 CVE-2021-37627 >= 4.0.0, < 4.4.56, >= 4.5.0, < 4.9.18, >= 4.10.0, < 4.11.7 4.4.56, 4.9.18, 4.11.7
  12. Unrestricted file uploads in Contao
    High · 8.8 CVE-2019-19745 >= 4.0.0, < 4.4.46, >= 4.5.0, < 4.8.6 4.4.46, 4.8.6

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