CVE-2026-87814Public exploitNetwork attack vector

Stored XSS via unescaped asset preview content

Published Sep 9, 2026 · Updated Sep 9, 2026

Stored XSS in SiYuan before 3.8.2 allows remote authenticated users to execute JavaScript when a victim previews a crafted text asset. The search asset preview handler returns raw UTF-8 bytes from /api/search/getAssetContent and concatenates assetContent.content into element.innerHTML without escaping or sanitization. An attacker must place the asset in a shared, synchronized, or imported workspace and induce a victim preview; execution inherits the SiYuan origin and can issue authenticated API requests or alter workspace content.

CVSS severity9.0
Critical
EPSS probability0.21%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stored XSS in SiYuan before 3.8.2 allows remote authenticated users to execute JavaScript when a victim previews a crafted text asset. The search asset preview handler returns raw UTF-8 bytes from /api/search/getAssetContent and concatenates assetContent.content into element.innerHTML without escaping or sanitization. An attacker must place the asset in a shared, synchronized, or imported workspace and induce a victim preview; execution inherits the SiYuan origin and can issue authenticated API requests or alter workspace content.

The record

CVE
CVE-2026-87814
Published
Sep 9, 2026
Updated
Sep 9, 2026
Vendor
SiYuan Note
Product
SiYuan
Classifications
CWE-79, T1204.002
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 9, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 9, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <3.8.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

SiYuan Note · SiYuanversion=0 <3.8.2

Published CVSS scores

8.4National Vulnerability DatabaseCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:A/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
9.0SiYuan NoteCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1204.002Malicious File

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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