External risk intelligence

SiYuan Bazaar Path Traversal Vulnerability

CVE advisorySeverity: CRITICAL (CVSS 9.4)

CVE-2026-77086

The vulnerability exists in administrative endpoints of the SiYuan application. While these functions are reachable over a network, they require authenticated administrative access, and the application is typically deployed for personal or private team use rather than as a public-facing service.

Path Traversal

Halo Surface Signal: 3 out of 5 — possibly public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

This vulnerability involves a flaw in the SiYuan application that could allow authenticated administrators to manipulate files on the system, posing a risk to data integrity and system security. The core issue lies in how the application handles package installation and uninstallation, where improper validation of a parameter could enable unauthorized file operations. The main concern is confirming relevance and exposure.

Admins could misuse install/uninstall features.
Unchecked file operations can impact system integrity.
Verify if this administrative function is in use.

Attack Path

How an attacker could exploit the issue

An attacker with administrator access to SiYuan could exploit this vulnerability by manipulating the `packageName` parameter in Bazaar's install or uninstall functions. This manipulation allows the attacker to traverse directories, enabling them to write arbitrary files to any location on the system or delete entire directories.

Requires authenticated administrator access.
Crafted `packageName` in Bazaar endpoints.
Arbitrary file write or directory deletion.

Live Threat

Current exploitation, exposure, and threat context

Authenticated administrators could leverage path traversal flaws to write arbitrary files or delete directories, potentially impacting the integrity and availability of the SiYuan application and its data. This occurs when crafting specific `packageName` values for Bazaar install and uninstall operations.

System files and directories at risk.
Authenticated administrators can exploit it.
Compromised application integrity and availability.

Operational Fix

Recommended remediation, mitigation, and detection steps

SiYuan administrators are responsible for managing Bazaar installations and should first confirm which instances are network-reachable and business-critical. This will help identify the accountable owner and inform a prioritized remediation plan.

SiYuan administrators own this issue.
Verify network reachability and criticality.
Plan vendor-assisted remediation.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

Halo Threat Intelligence helps prioritize remediation with Halo Surface Signal and H/A/L/O context. Start exposure validation with a free external attack surface trial.

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Frequently asked questions

What is SiYuan?

SiYuan is a local-first, privacy-focused note-taking application that supports structured data and block-level referencing. It often serves as a personal knowledge management tool or a collaborative workspace for small teams. The application includes a "Bazaar" feature that allows users to extend its core functionality by installing and managing various plugins or packages.

What is the path traversal weakness in CVE-2026-77086?

This vulnerability is classified as CWE-22, which involves improper validation of user-supplied paths. In SiYuan, the software fails to sanitize the packageName input used during Bazaar package operations. This allows a user to include directory traversal sequences—such as '../'—to break out of the intended folder, granting the ability to write files or delete directories anywhere the application has system permissions.

Can this be triggered without admin access?

No. The vulnerability specifically affects administrative endpoints related to the Bazaar install and uninstall functions. An attacker must already possess authenticated administrator access to the SiYuan instance to supply the malicious input. Providing a standard, valid package name to these endpoints will not trigger the bug; the exploit requires intentionally crafted input designed to navigate the file system.

Is my instance relevant according to Halo Surface Signal?

While the vulnerability resides in administrative endpoints that are reachable over a network, Halo Surface Signal notes that SiYuan is typically deployed for private use rather than as a public-facing service. Relevance depends on whether your specific instance is accessible to untrusted users over the internet, as an attacker would need both administrative credentials and network access to succeed.

How do I respond to CVE-2026-77086?

The most effective response is to update your SiYuan installation to version 3.7.4 or later, where this validation flaw is resolved. If an immediate update is not possible, prioritize restricting network access to your administrative interface. You should also audit your current administrative accounts to ensure that only authorized, trusted users have access to the application's configuration and Bazaar management features.

References

Written by Nicholas Merritt

Nicholas Merritt is VP of Security Solutions at Halo Security. With more than 25 years across application security, vulnerability prioritization, and offensive security, he helps teams translate threat data into practical exposure validation and remediation focus. He authors Halo Threat Intelligence CVE advisories using Halo Surface Signal and H/A/L/O context to prioritize internet-facing risk.