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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 在 v3.8.2 之前版本中存在存储型跨站脚本（XSS）漏洞。该漏洞源于资产服务中的扩展名黑名单不完整，遗漏了若干可执行脚本的文件类型。攻击者可上传扩展名为 .xht、.ehtml、.xsl、.xbl 或 .rdf 的文件；这些扩展名会被解析为支持脚本执行的内容类型，从而允许 JavaScript 代码被执行。借此，攻击者能够窃取 API 令牌并进一步攻破工作区。

CVSS 9.0 · Critical EPSS 0.23% · P14

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

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

V. Comments for CVE-2026-84803

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