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Fencer Intel
medium 5.3

CVE-2026-107843 json

Contao: The registration module re-sends activation mails on any unauthenticated POST, with no throttle and no captcha check

published last mo. modified 24d ago also EUVD-2026-95973 , GHSA-mfxh-vp55-7gc6

cvss
5.3
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 19%
public exploits
0
none known

Summary

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.

Patch / fix

  • packagist contao/core-bundle 5.3.50, 5.7.12
  • contao contao_cms 5.3.50, 5.7.12
  • contao contao 5.3.50, 5.7.12

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CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
27d ago

Exploit prediction

0.27% chance of exploitation in the next 30 days, higher than 19% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CNA 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
GitHub 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

Affected packages

ecosystem package affected fixed in
packagist contao/core-bundle
>=4.1.0, <5.3.50
>=5.4.0-RC1, <5.7.12
5.3.50
5.7.12

Affected products

  • contao contao

Classification

Weakness
  • CWE-204 Observable Response Discrepancy
  • CWE-770 Allocation of Resources Without Limits or Throttling

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.