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Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')


Severity Medium
Score 6.1/10


TYPO3 is a free and open-source Content Management Framework released under the GNU General Public License. In affected packages, typo3/cms, typo3/cms-core and typo3/cms-frontend versions 8.7.x prior to 8.7.51, 9.0.x prior to 9.5.40, 10.0.x prior to 10.4.35, 11.0.x prior to 11.5.23, and 12.0.x prior to 12.2.0 the TYPO3 core component "GeneralUtility::getIndpEnv()" uses the unfiltered server environment variable "PATH_INFO", which allows attackers to inject malicious content. In combination with the TypoScript setting "config.absRefPrefix=auto", attackers can inject malicious HTML code to pages that have not been rendered and cached, yet. As a result, injected values would be cached and delivered to other website visitors (persisted cross-site scripting). Individual code which relies on the resolved value of "GeneralUtility::getIndpEnv('SCRIPT_NAME')" and corresponding usages (as shown below) are vulnerable as well. Additional investigations confirmed that at least Apache web server deployments using CGI (FPM, FCGI/FastCGI, and similar) are affected. However, there still might be the risk that other scenarios like nginx, IIS, or "Apache/mod_php" are vulnerable. The usage of server environment variable "PATH_INFO" has been removed from corresponding processings in "GeneralUtility::getIndpEnv()". Besides that, the public property "TypoScriptFrontendController::$absRefPrefix" is encoded for both being used as a URI component and for being used as a prefix in an HTML context. This mitigates the cross-site scripting vulnerability. For users who are unable to patch in a timely manner the TypoScript setting "config.absRefPrefix" should at least be set to a static path value, instead of using auto - e.g. "config.absRefPrefix=/". This workaround **does not fix all aspects of the vulnerability**, and is just considered to be intermediate mitigation to the most prominent manifestation.

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CWE-79 - Cross Site Scripting

Cross-Site Scripting, commonly referred to as XSS, is the most dominant class of vulnerabilities. It allows an attacker to inject malicious code into a pregnable web application and victimize its users. The exploitation of such a weakness can cause severe issues such as account takeover, and sensitive data exfiltration. Because of the prevalence of XSS vulnerabilities and their high rate of exploitation, it has remained in the OWASP top 10 vulnerabilities for years.

Advisory Timeline

  • Published