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CVE-2026-84803— SiYuan before v3.8.2 Stored XSS via incomplete asset blocklist

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团队开源的一个以隐私为先的个人知识管理系统。 SiYuan 3.8.2之前版本存在跨站脚本漏洞，该漏洞源于资源服务中扩展名黑名单不完整，遗漏了可执行脚本的文件类型，可能导致攻击者上传.xht、.ehtml、.xsl、.xbl或.rdf等扩展名的文件，执行JavaScript窃取API令牌并破坏工作区。

CVSS 9.0 · Critical EPSS 0.43% · P36

Possible ATT&CK Techniques 1 AI

T1059 · Command and Scripting Interpreter

Affected Version Matrix 2

VendorProduct Version RangeStatus
siyuan-note siyuan < 3.8.2 affected
3.8.2 unaffected
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I. Basic Information for CVE-2026-84803

Vulnerability Information
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Vulnerability Title
SiYuan before v3.8.2 Stored XSS via incomplete asset blocklist
Source: CVE Program / CVE List V5
Vulnerability Description
SiYuan before v3.8.2 contains a stored cross-site scripting vulnerability in asset serving due to an incomplete extension blocklist that misses script-capable file types. Attackers can upload files with extensions like .xht, .ehtml, .xsl, .xbl, or .rdf that resolve to executable media types and execute JavaScript to steal API tokens and compromise workspaces.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
在Web页面生成时对输入的转义处理不恰当(跨站脚本)
Source: CVE Program / CVE List V5
Vulnerability Title
SiYuan 跨站脚本漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
SiYuan是SiYuan团队开源的一个以隐私为先的个人知识管理系统。 SiYuan 3.8.2之前版本存在跨站脚本漏洞，该漏洞源于资源服务中扩展名黑名单不完整，遗漏了可执行脚本的文件类型，可能导致攻击者上传.xht、.ehtml、.xsl、.xbl或.rdf等扩展名的文件，执行JavaScript窃取API令牌并破坏工作区。
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)

Affected Products

Vendor Product Affected Versions CPE Subscribe
siyuan-note siyuan 0 ~ 3.8.2 -

II. Public POCs for CVE-2026-84803

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III. Intelligence Information for CVE-2026-84803

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Vendor Advisories for CVE-2026-84803 (2)

IV. Related Vulnerabilities

Same product: siyuan
Same vendor: siyuan-note
Same weakness: CWE-79