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CVE-2026-31809

SiYuan has a SVG Sanitizer Bypass via Whitespace in `javascript:` URI — Unauthenticated XSS

Published: Mar 10, 2026Updated: Mar 11, 2026 Sources: CVE List NVD GHSACWE-79
NVD MITRE
6.1CVSSMEDIUM
EPSS Score
0.5%
Top 60.9%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
Patch Available
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Description

SiYuan is a personal knowledge management system. Prior to 3.5.10, SiYuan's SVG sanitizer (SanitizeSVG) checks href attributes for the javascript: prefix using strings.HasPrefix(). However, inserting ASCII tab (	), newline (
), or carriage return (
) characters inside the javascript: string bypasses this prefix check. Browsers strip these characters per the WHATWG URL specification before parsing the URL scheme, so the JavaScript still executes. This allows an attacker to inject executable JavaScript into the unauthenticated /api/icon/getDynamicIcon endpoint, creating a reflected XSS. This is a second bypass of the fix for CVE-2026-29183 (fixed in v3.5.9). This vulnerability is fixed in 3.5.10.

CVSS Vector Breakdown

AV:NAC:LPR:NUI:RS:CC:LI:LA:N
Exploitability
AV:NAttack Vector
Network
AC:LAttack Complexity
Low
PR:NPrivileges Required
None
UI:RUser Interaction
Required
Scope
S:CScope
Changed
Impact
C:LConfidentiality
Low
I:LIntegrity
Low
A:NAvailability
None
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Weaknesses

CWE-79

Affected Products

siyuansiyuan-note
siyuanb3log
On-premWeb App
Web & CMS Plugins / cms-core
github.com/siyuan-note/siyuan/kernelGoOSS Libraries
b3logoss-projectWeb & CMS Pluginsaka b3log
gopackage-ecosystemOSS Libraries

Attack Graph

Products CVE Techniques Tactics

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Exploitability

Official Patch Available

MITRE ATT&CK

2 techniques
Execution
Initial Access
View detailed technique mapping

References

https://github.com/siyuan-note/siyuan/security/advisories/GHSA-pmc9-f5qr-2pcr
github.com
https://nvd.nist.gov/vuln/detail/CVE-2026-31809
nvd.nist.gov
https://github.com/siyuan-note/siyuan
github.com
and 1 more references View all →

Timeline

Published
Mar 10, 2026
Last Updated
Mar 11, 2026

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