Open Redirect in TYPO3 CMS via Sanitized Local URL

Compliance Impact

This vulnerability allows attackers to perform open redirect attacks by redirecting users to external malicious websites, potentially enabling phishing attacks.

Such phishing attacks can lead to unauthorized disclosure of personal or sensitive information, which may impact compliance with data protection regulations like GDPR and HIPAA that require safeguarding user data and preventing unauthorized access.

Therefore, if exploited, this vulnerability could undermine an organization's ability to comply with these standards by exposing users to phishing risks and potential data breaches.

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Executive Summary

This vulnerability exists in TYPO3 CMS where the function GeneralUtility::sanitizeLocalUrl, intended to allow only local URLs, does not properly sanitize URLs. As a result, attackers can exploit this flaw to perform open redirect attacks by redirecting users to external, potentially malicious websites.

The issue arises because the sanitization checks do not sufficiently validate the URL characters, allowing URLs with invalid characters, whitespace, or control characters to pass through. This enables attackers to manipulate URLs to redirect users to phishing or malicious sites.

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Impact Analysis

This vulnerability can impact users by enabling attackers to redirect them from trusted TYPO3 CMS websites to external malicious sites. Such redirections can be used for phishing attacks, where attackers attempt to steal sensitive information by impersonating legitimate sites.

Because the redirect occurs after the URL passes sanitization, users may be tricked into trusting the link, increasing the risk of credential theft, malware infection, or other malicious activities.

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Detection Guidance

This vulnerability involves open redirect attacks via improperly sanitized URLs in TYPO3 CMS. Detection involves monitoring for suspicious URL redirection patterns or attempts to use malformed URLs that bypass sanitization.

You can detect potential exploitation attempts by searching web server logs for unusual redirect URLs or URLs containing invalid characters such as backslashes, spaces, or control characters.

• Use grep or similar tools to find suspicious redirect parameters in logs, for example: grep -E 'redirect=|url=' /var/log/apache2/access.log
• Look for URLs containing backslashes or encoded spaces that might indicate attempts to exploit the vulnerability: grep -P '\\|%20' /var/log/apache2/access.log
• Monitor application logs for warnings or errors related to URL sanitization failures, as the patched function logs rejected URLs with invalid characters.

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Mitigation Strategies

The primary mitigation step is to update TYPO3 CMS to a patched version that fixes the vulnerability.

• Upgrade to TYPO3 CMS versions 10.4.57 ELTS, 11.5.51 ELTS, 12.4.46 ELTS, 13.4.31 LTS, or 14.3.3 LTS or later.

These updates include stricter URL validation in the GeneralUtility::sanitizeLocalUrl function, which rejects URLs with invalid characters and prevents open redirect attacks.

Additionally, review and restrict URL redirection logic in your application to ensure only trusted local URLs are accepted.

Subscribe to the typo3-announce mailing list and consult the TYPO3 Security Guide for ongoing security recommendations.

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