CVE-2026-110774 in Blinko
Summary
by MITRE • 10/14/2026
Blinko through 1.8.8 contains a broken access control vulnerability in the /api/file route that allows authenticated users to read other users' private attachments due to a flawed owner check. Attackers can supply another user's stored filename, following a basename plus millisecond-timestamp pattern, to download private, non-shared attachments.
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Analysis
by VulDB Data Team • 10/14/2026
The identified security flaw resides within the Blinko application, specifically affecting versions up through 1.8.8, and centers on a critical failure in access control mechanisms governing file retrieval operations. The vulnerability is located at the /api/file endpoint, which serves as the primary interface for accessing stored attachments. In secure systems of this nature, it is imperative that any request to retrieve sensitive data be rigorously validated against the identity of the requesting user and the ownership attributes of the target resource. However, in this instance, the server-side logic responsible for verifying whether a user has permission to access a specific file relies on an insufficient owner check mechanism. This logical deficiency means that while the system may authenticate the user's session, it fails to adequately cross-reference the authenticated identity with the actual ownership metadata of the requested attachment before granting access.
The technical exploitation of this vulnerability leverages a predictable naming convention used by the application for storing files. Blinko employs a pattern consisting of a basename followed by a millisecond-timestamp to generate unique filenames for attachments. This deterministic structure allows an attacker who has valid credentials for one account to enumerate or guess filenames associated with other users' accounts. By supplying another user's stored filename, which follows this known format, the malicious actor can trigger the /api/file route without triggering any access denial errors. Because the backend validation logic does not strictly enforce that the file being requested belongs exclusively to the authenticated session holder, the server processes the request and returns the private attachment data. This constitutes a classic Insecure Direct Object Reference scenario where sequential or predictable identifiers are used to bypass authorization checks.
From an operational impact perspective, this broken access control vulnerability results in a severe compromise of confidentiality for all users within the Blinko ecosystem. Since attachments often contain sensitive personal documents, images, or other private data, unauthorized access by any authenticated user leads to significant privacy violations and potential exposure of proprietary information. The risk is exacerbated by the fact that the attack does not require privilege escalation beyond standard authentication; it exploits a logic flaw accessible to any valid account holder. This could facilitate further attacks such as social engineering using leaked personal documents or data aggregation for malicious purposes, thereby undermining trust in the platform's security posture and potentially violating regulatory compliance requirements regarding data protection and user privacy.
To mitigate this vulnerability, immediate remediation is required by developers of Blinko prior to version 1.8.9 release. The core fix must involve implementing robust server-side authorization checks that explicitly verify ownership permissions for every file access request. This should include validating the resource identifier against a secure database record linked to the authenticated user's unique identity token, rather than relying solely on filename patterns or client-supplied data. Additionally, adopting non-sequential, cryptographically random identifiers for stored files would mitigate the risk of enumeration attacks based on timestamp-based naming conventions. Security teams managing Blinko deployments should also consider implementing strict logging and monitoring for anomalous file access patterns to detect potential exploitation attempts in real-time until patches are applied.
This vulnerability aligns with CWE-284, which describes Improper Access Control, specifically highlighting failures where authorization checks are bypassed due to flawed logic or insufficient validation of object ownership. Furthermore, the attack vector corresponds to MITRE ATT&CK technique T1078, Valid Accounts, as it relies on legitimate credentials combined with a logical flaw in resource access permissions rather than exploiting software bugs like buffer overflows or injection flaws. Addressing this issue requires both immediate code correction and long-term architectural improvements to ensure that all data retrieval operations are subject to rigorous identity verification and permission validation protocols consistent with industry best practices for secure application development.