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CVE-2026-25539— SiYuan has Arbitrary File Write via /api/file/copyFile leading to RCE

Quick assessment

Affected
siyuan-note siyuan
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

SiYuan是SiYuan开源的一个隐私至上的个人知识管理系统。 SiYuan 3.5.5之前版本存在路径遍历漏洞，该漏洞源于/api/file/copyFile端点未验证dest参数，可能导致写入文件至任意位置，进而引发远程代码执行。

CVSS 9.1 · Critical EPSS 1.13% · P66
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I. Basic Information for CVE-2026-25539

Vulnerability Information
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Vulnerability Title
SiYuan has Arbitrary File Write via /api/file/copyFile leading to RCE
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
对路径名的限制不恰当(路径遍历)
Source: CVE Program / CVE List V5
Vulnerability Title
SiYuan 路径遍历漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
SiYuan是SiYuan开源的一个隐私至上的个人知识管理系统。 SiYuan 3.5.5之前版本存在路径遍历漏洞，该漏洞源于/api/file/copyFile端点未验证dest参数，可能导致写入文件至任意位置，进而引发远程代码执行。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

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Affected Products

Vendor Product Affected Versions CPE Subscribe
siyuan-note siyuan < 3.5.5 -

II. Public POCs for CVE-2026-25539

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III. Intelligence Information for CVE-2026-25539

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Vendor Advisories for CVE-2026-25539 (1)

IV. Related Vulnerabilities

Same product: siyuan
Same vendor: siyuan-note
Same weakness: CWE-22

V. Comments for CVE-2026-25539

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