CVE-2026-31809Public exploitNetwork attack vector

Reflected XSS via whitespace-obscured JavaScript URI

Published Mar 10, 2026 · Updated Mar 10, 2026

Reflected XSS in SiYuan before 3.5.10 allows remote attackers to execute JavaScript in its application origin via a crafted icon URL. SanitizeSVG decodes href entities but checks only a literal javascript: prefix, leaving internal ASCII tabs, newlines, or carriage returns that browsers discard. The unauthenticated endpoint returns the crafted SVG, but a user must open the URL and click its link before script can access session data or issue authenticated API calls.

CVSS severity6.1
Medium
EPSS probability0.51%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Reflected XSS in SiYuan before 3.5.10 allows remote attackers to execute JavaScript in its application origin via a crafted icon URL. SanitizeSVG decodes href entities but checks only a literal javascript: prefix, leaving internal ASCII tabs, newlines, or carriage returns that browsers discard. The unauthenticated endpoint returns the crafted SVG, but a user must open the URL and click its link before script can access session data or issue authenticated API calls.

The record

CVE
CVE-2026-31809
Published
Mar 10, 2026
Updated
Mar 10, 2026
Vendor
SiYuan Note
Product
SiYuan
Classifications
CWE-79, T1204.001
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 10, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 10, 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=< 3.5.10

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

SiYuan Note · SiYuanversion=< 3.5.10

Published CVSS scores

6.4GitHubCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N
6.1NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/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.

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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1204.001Malicious Link

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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