TYPO3 freeCap CAPTCHA Extension CVE-2019-16699 Remote Code Execution Vulnerability



Date Discovered

October 15, 2019


TYPO3 freeCap CAPTCHA extension is prone to a remote code-execution vulnerability. A remote attacker can leverage this issue to execute arbitrary code within the context of the application. Successful exploits will compromise the application and possibly the underlying system. Versions prior to freeCap CAPTCHA 2.4.6 and 2.5.3 are vulnerable.

Technologies Affected

  • Typo3 freeCap CAPTCHA 1.2.1
  • Typo3 freeCap CAPTCHA 1.2.2
  • Typo3 freeCap CAPTCHA 1.2.3
  • Typo3 freeCap CAPTCHA 2.4.5
  • Typo3 freeCap CAPTCHA 2.5.2


Block external access at the network boundary, unless external parties require service.
If global access isn't needed, filter access to the affected computer at the network boundary. Restricting access to only trusted computers and networks might greatly reduce the likelihood of successful exploits.

Run all software as a nonprivileged user with minimal access rights.
To reduce the impact of latent vulnerabilities, run the application with the minimal amount of privileges required for functionality.

Deploy network intrusion detection systems to monitor network traffic for malicious activity.
Deploy NIDS to monitor network traffic for signs of anomalous or suspicious activity including unexplained incoming and outgoing traffic. This may indicate exploit attempts or activity that results from successful exploits.

Do not accept or execute files from untrusted or unknown sources.
To reduce the likelihood of successful exploits, never handle files that originate from unfamiliar or untrusted sources.

Updates are available. Please see the references or vendor advisory for more information.



Kai Ullrich, Code White GmbH

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