CVE-2026-31809 MEDIUM

CVE-2026-31809: SiYuan has a SVG Sanitizer Bypass via Whitespace in `javascript:` URI — Unauthenticated XSS

Vendor Siyuan-Note

Product siyuan

Weakness CWE-79 · XSS

Published March 10, 2026

Last update March 11, 2026

View on NVD All CVEs

CVSS base score

6.4/10

Attack vector Network

Attack complexity Low

Privileges required None

User interaction —

Confidentiality —

Integrity —

CVSS vector

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N

What the vulnerability does

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.

Key dates

Disclosure timeline

March 10, 2026 CVE published

March 11, 2026 Record updated