CVE-2026-31809
However, inserting ASCII tab (	), newline ( ), or carriage return ( ) characters inside the javascript: string bypasses this prefix check.
Does this matter?
Lower severity and a low EPSS score (0.51%). Track it; it rarely justifies an emergency change on its own.
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 4.0
- 6.4 MEDIUMCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/M
- EPSS
- 0.51% probability · 42th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-79
- Affected
- b3log/siyuan
- Source
- security-advisories@github.com
References
- https://github.com/siyuan-note/siyuan/security/advisories/GHSA-pmc9-f5qr-2pcrExploit, Vendor Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.