Open Redirect Vulnerability in Dub Short Links

Executive Summary

Dub has an open redirect vulnerability where the redir_url query parameter is accepted on every short link without validation or domain allowlist enforcement. Attackers can append this parameter to any short link to redirect visitors to arbitrary external URLs through the trusted Dub domain, bypassing destination blacklists and enabling phishing attacks with link cloaking.

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Detection Guidance

To detect this vulnerability, monitor network traffic for Dub short links containing the redir_url parameter. Check HTTP logs for URLs with suspicious external domains appended to legitimate Dub links. Use tools like curl to test if a Dub short link redirects to an arbitrary domain by appending redir_url=https://example.com to a valid short link.

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Impact Analysis

This vulnerability allows attackers to trick users into visiting malicious websites by redirecting them from a trusted Dub domain. Users may unknowingly disclose sensitive information or install malware. Organizations using Dub for link shortening may face reputational damage and increased risk of phishing attacks targeting their users.

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Compliance Impact

This vulnerability could lead to compliance violations under GDPR or HIPAA if user data is exposed due to phishing attacks or unauthorized redirects. Organizations may fail to protect user data adequately, resulting in regulatory penalties or legal consequences.

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Mitigation Strategies

Implement input validation to restrict redir_url to trusted domains only. Add a domain allowlist for redirection targets. Update Dub configurations to enforce strict URL validation. Monitor and block any requests with unapproved redir_url parameters.

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