CVE-2026-31809 | THREATINT

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.

PUBLISHED Reserved 2026-03-09 | Published 2026-03-10 | Updated 2026-03-11 | Assigner GitHub_M

MEDIUM: 6.4CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N

Problem types

CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Product status

< 3.5.10

affected

References

github.com/...siyuan/security/advisories/GHSA-pmc9-f5qr-2pcr

cve.org (CVE-2026-31809)

nvd.nist.gov (CVE-2026-31809)

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