CVE-2026-25539
Unknown Unknown - Not Provided
Path Traversal in SiYuan File API Enables Remote Code Execution

Publication date: 2026-02-04

Last updated on: 2026-02-11

Assigner: GitHub, Inc.

Description
SiYuan is a personal knowledge management system. Prior to version 3.5.5, the /api/file/copyFile endpoint does not validate the dest parameter, allowing authenticated users to write files to arbitrary locations on the filesystem. This can lead to Remote Code Execution (RCE) by writing to sensitive locations such as cron jobs, SSH authorized_keys, or shell configuration files. This issue has been patched in version 3.5.5.
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Meta Information
Published
2026-02-04
Last Modified
2026-02-11
Generated
2026-06-16
AI Q&A
2026-02-05
EPSS Evaluated
2026-06-15
NVD
CVE-2026-25539
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
b3log siyuan to 3.5.3 (inc)
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-22 The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.
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Executive Summary

The vulnerability exists in SiYuan, a personal knowledge management system, specifically in versions prior to 3.5.5. The /api/file/copyFile endpoint does not properly validate the 'dest' parameter, which allows authenticated users to write files to arbitrary locations on the filesystem.

Because of this lack of validation, an attacker can write files to sensitive locations such as cron jobs, SSH authorized_keys, or shell configuration files, potentially leading to Remote Code Execution (RCE).

This vulnerability was fixed in version 3.5.5.

Impact Analysis

This vulnerability can have severe impacts because it allows an authenticated user to execute arbitrary code remotely by writing files to sensitive system locations.

  • Remote Code Execution (RCE) can lead to full system compromise.
  • Attackers can modify cron jobs to execute malicious tasks automatically.
  • Attackers can add SSH authorized keys to gain persistent access.
  • Modifying shell configuration files can allow attackers to maintain control or escalate privileges.
Compliance Impact

I don't know

Detection Guidance

I don't know

Mitigation Strategies

The immediate step to mitigate this vulnerability is to upgrade SiYuan to version 3.5.5 or later, where the issue has been patched.

Since the vulnerability allows authenticated users to write files to arbitrary locations, restricting access to the /api/file/copyFile endpoint and limiting user privileges can also help reduce risk until the patch is applied.

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