CVE-2026-103763 in SiYuan
Summary
by MITRE • 10/02/2026
SiYuan before v3.8.5 contains an information disclosure vulnerability that allows read-only publish readers to learn metadata of publish-excluded documents through the getNotebookInfo endpoint. Attackers, including anonymous visitors when no reader password is set, can query publish-visible notebooks to obtain document count, size and modification timestamps of hidden documents.
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Analysis
by VulDB Data Team • 10/02/2026
The identified vulnerability in SiYuan versions prior to 3.8.5 represents a significant information disclosure flaw within the application's publishing mechanism. This security issue stems from an insufficient access control implementation on the getNotebookInfo API endpoint, which is designed to provide metadata about notebooks that are made publicly accessible via the platform's publish feature. The core technical failure lies in the server-side logic processing requests for this specific endpoint; it fails to adequately filter or exclude documents that have been explicitly marked as hidden from public view within the notebook structure. Consequently, when an authenticated user with read-only publishing privileges—or even an anonymous visitor if no reader password is configured—queries a publish-visible notebook, the backend returns comprehensive metadata including document counts, file sizes, and modification timestamps for all contained items, regardless of their visibility settings. This behavior effectively bypasses the intended privacy controls established by the content creator, exposing internal structural details that should remain opaque to external observers.
From an operational perspective, this vulnerability allows attackers to perform reconnaissance against targeted SiYuan instances with minimal effort. By leveraging standard HTTP requests to the getNotebookInfo endpoint, adversaries can enumerate hidden documents and gather intelligence about their existence without needing elevated privileges or authentication credentials in many configurations. The exposure of metadata such as modification timestamps and file sizes can facilitate further attacks by revealing patterns in user activity, identifying potentially sensitive content based on naming conventions inferred from size variations, or timing subsequent exploitation attempts to coincide with periods of high activity indicated by timestamp anomalies. Although the vulnerability is classified as read-only and does not directly allow for data exfiltration of document contents, it significantly degrades the confidentiality guarantees expected by users who rely on SiYuan's publishing features to share selected information while keeping other parts private.
This flaw aligns with CWE-200, which categorizes Information Exposure, specifically reflecting scenarios where sensitive system or application details are accessible to unauthorized actors due to misconfigured access controls. In the context of the MITRE ATT&CK framework, this vulnerability supports reconnaissance tactics by enabling adversaries to gather information about the target environment's structure and content organization. The ability to discover hidden resources through metadata leakage is a common precursor to more severe intrusions, as it provides attackers with a map of potential targets within an application that they might otherwise not know exists.
To mitigate this risk, users must upgrade SiYuan to version 3.8.5 or later, where the developers have addressed the access control logic on the getNotebookInfo endpoint to properly respect document visibility settings. Until such updates are applied, administrators should consider implementing additional network-level controls if possible, although application-layer fixes remain the primary defense. It is also advisable to enforce reader passwords for all published notebooks to add a layer of authentication that restricts metadata access to verified users only, thereby reducing the attack surface available to anonymous actors. Regular security audits and adherence to principle of least privilege in API design are essential practices to prevent similar information disclosure issues in future updates.