Broken Access Control in Blinko Allows Unauthorized File Access

Executive Summary

CVE-2026-110774 is a broken access control vulnerability in Blinko through version 1.8.8. It allows authenticated users to read private attachments belonging to other users via the /api/file route. The flaw stems from improper ownership verification, enabling attackers to access non-shared files by supplying a predictable filename format (basename plus millisecond-timestamp).

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Detection Guidance

To detect this vulnerability, check if authenticated users can access private attachments via the /api/file route by requesting files with another user's filename pattern (basename plus millisecond-timestamp). Monitor logs for unauthorized file access attempts or unusual API calls to /api/file with non-owned filenames.

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Impact Analysis

This vulnerability allows unauthorized users to access private files such as images or documents uploaded by others. While it does not permit write, update, or delete operations, it breaches cross-user confidentiality. Attackers with low privileges or API tokens can exploit it to view sensitive data.

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Compliance Impact

This vulnerability could lead to non-compliance with data protection regulations like GDPR and HIPAA due to unauthorized access to private user data. It violates principles of data confidentiality and user consent, potentially resulting in legal and regulatory penalties.

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Mitigation Strategies

Immediately update Blinko to the latest version beyond 1.8.8. Implement strict ownership verification in the /api/file route by replacing the flawed condition with an explicit check ensuring only the owner or authorized users can access files. Review logs for past unauthorized access and restrict API token permissions.

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