CVE-2026-66394Public exploitNetwork attack vectorHinoki check available

Stored and reflected XSS via SVG parser confusion

Published Jul 27, 2026 · Updated Jul 27, 2026

Cross-site scripting in SiYuan before 3.7.3 allows remote authenticated users to execute scripts through sanitized SVG content. The util.SanitizeSVG cleaner parses SVG as HTML, so scripts nested in raw-text descendants survive and execute when browsers parse the response as XML. Reader-level access and victim navigation or embedding are sufficient; execution in the application origin can read or alter notes and steal the API token.

CVSS severity9.3
Critical
EPSS probability0.27%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Cross-site scripting in SiYuan before 3.7.3 allows remote authenticated users to execute scripts through sanitized SVG content. The util.SanitizeSVG cleaner parses SVG as HTML, so scripts nested in raw-text descendants survive and execute when browsers parse the response as XML. Reader-level access and victim navigation or embedding are sufficient; execution in the application origin can read or alter notes and steal the API token.

The record

CVE
CVE-2026-66394
Published
Jul 27, 2026
Updated
Jul 27, 2026
Vendor
SiYuan Note
Product
SiYuan
Classifications
CWE-79, T1203
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jul 27, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 27, 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 <3.7.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

SiYuan Note · SiYuanversion=0 <3.7.3

Published CVSS scores

9.3VulnCheckCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:H/VI:H/VA:N/SC:H/SI:H/SA:N
8.7VulnCheckCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A: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.

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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')
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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