CVE-2026-84803Public exploitNetwork attack vectorHinoki check available

Workspace compromise via incomplete asset extension blocklist

Published Sep 2, 2026 · Updated Sep 2, 2026

Stored XSS in SiYuan before 3.8.2 allows remote authenticated users to compromise workspaces through script-capable assets. The isAssetInlineUnsafe function in kernel/server/serve.go treats recognized extensions absent from its blocklist as safe for inline serving, omitting Content-Disposition for executable XML and HTML aliases. An authenticated user must place and open such an asset; same-origin script can then steal the API token and gain persistent read and write access to workspace data.

CVSS severity8.6
High
EPSS probability0.23%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Stored XSS in SiYuan before 3.8.2 allows remote authenticated users to compromise workspaces through script-capable assets. The isAssetInlineUnsafe function in kernel/server/serve.go treats recognized extensions absent from its blocklist as safe for inline serving, omitting Content-Disposition for executable XML and HTML aliases. An authenticated user must place and open such an asset; same-origin script can then steal the API token and gain persistent read and write access to workspace data.

The record

CVE
CVE-2026-84803
Published
Sep 2, 2026
Updated
Sep 2, 2026
Vendor
SiYuan Note
Product
SiYuan
Classifications
CWE-184, CWE-79, T1203
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 2, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 2, 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

9.0VulnCheck CNACVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H
8.6VulnCheck CNACVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-184Incomplete List of Disallowed Inputs
CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1203Exploitation for Client Execution

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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