TYPO3 CMS Webhooks Server Side Request Forgery

Problem

Webhooks are inherently vulnerable to Server-Side Request Forgery (SSRF), which can be exploited by adversaries to target internal resources (e.g., localhost or other services on the local network). While this is not a vulnerability in TYPO3 itself, it may enable attackers to blindly access systems that would otherwise be inaccessible. An administrator-level backend user account is required to exploit this vulnerability.

Solution

Update to TYPO3 versions 12.4.31 LTS, 13.4.12 LTS that fix the problem described.

[!IMPORTANT]

Manual actions required

To mitigate potential SSRF risks via webhooks, it is recommended to explicitly allow access only to trusted hosts. This can be achieved by configuring the allowlist in $GLOBALS['TYPO3_CONF_VARS']['HTTP']['allowed_hosts']['webhooks'].

If the allowlist is not defined or set to null, all requests will be allowed. If the allowlist is an empty array, all requests will be blocked.

By default, the factory setting allows all requests. This prevents existing webhooks from failing after upgrading to the affected TYPO3 versions. Administrators must configure this setting manually to enforce restrictions.

Credits

Thanks to the National Cyber Security Center (NCSC) of Switzerland for reporting this issue, and to TYPO3 core & security team member Benjamin Franzke for fixing it.