TYPO3-EXT-SA-2026-022: Server-Side Template Injection (SSTI) in extension "powermail" (powermail)
It has been discovered that the extension "powermail" (powermail) is vulnerable to Server-Side Template Injection (SSTI).
- Release Date: August 25, 2026
- Component Type: Third party extension. This extension is not a part of the TYPO3 default installation.
- Component: "powermail" (powermail)
- Composer Package Name: in2code/powermail
- Vulnerability Type: Server-Side Template Injection (SSTI)
- Affected Versions: 10.9.2 and below, 11.0.0 - 12.6.0, 13.0.0 - 13.2.0
- Severity: Critical
- Suggested CVSS v4.0: AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:A
- References: CVE-2026-77136, CWE-1336
Problem Description
The extension passes the raw value of a form field configured as "This field contains the name of the sender" directly into a Fluid View as template source, without any sanitization, and renders it. An anonymous, unauthenticated user can submit Fluid template syntax in that field to execute arbitrary Fluid ViewHelpers leading to disclosure of server configuration, environment variables and application source, and potentially remote code execution.
Exploitation requires only that a form field is configured as the “sender_name” field, a common and default-adjacent Powermail configuration. No authentication or user interaction beyond a normal form submission is required.
Note: This vulnerability is reported to be actively exploited in the wild. Users are strongly advised to update or apply mitigations immediately, independent of a full update.
Detection Guidance
Check received emails or the “sender_name” field possibly saved in the tx_powermail_domain_model_mail database table for any occurrences of Fluid syntax like f:, v: or namespace. Their presence indicates possible ViewHelper execution and exposure of sensitive information. If found, treat the system as potentially compromised and analyze and possibly repair the system carefully.
Solution
Updated versions 10.9.3, 12.6.1 and 13.2.1 are available from the TYPO3 extension manager, packagist and at
https://extensions.typo3.org/extension/download/powermail/13.2.1/zip
https://extensions.typo3.org/extension/download/powermail/12.6.1/zip
https://extensions.typo3.org/extension/download/powermail/10.9.3/zip
Users of the extension are advised to update the extension as soon as possible.
Users of the extension, for which no update is available, must ensure that the form field configuration “This field contains the name of the sender” is disabled.
Credits
Thanks to Antariksha Sharma, Rémi Payette, Office québécois de la langue française (OQLF) and Centre gouvernemental de Cyberdéfense (CGCD) for reporting the vulnerability, and to Marcus Schwemer for providing updated versions of the extension.
General Advice
Follow the recommendations that are given in the TYPO3 Security Guide.
