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

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

6.4 · 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 · score source

EPSS

• CVE-2026-31809: 0.52% estimated exploitation activity in the next 30 days; percentile 44.02 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

SVG Sanitizer Bypass via Whitespace in javascript: URI — Unauthenticated XSS Summary SiYuan's SVG sanitizer (SanitizeSVG) checks href attributes for the javascript: prefix using strings.HasPrefix(). However, inserting ASCII tab (&#9;), newline (&#10;), or carriage return (&#13;) 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), distinct from the <animate element bypass. Affected Component - File: kernel/util/misc.go - Function: SanitizeSVG() (lines 234-319) - Specific check: Line 271 — strings.HasPrefix(val, "javascript:") - Endpoint: GET /api/icon/getDynamicIcon?type=8&content=... (unauthenticated) - Version: SiYuan <= 3.5.9…

Published by the source

10 Mar 2026, 23:57 UTC

Last modified by the source

10 Mar 2026, 23:57 UTC

Source last checked

26 Oct 2026, 15:15 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-pmc9-f5qr-2pcr

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# Patch Next advisory brief: CVE-2026-31809

Advisory: SiYuan has a SVG Sanitizer Bypass via Whitespace in `javascript:` URI — Unauthenticated XSS
IDs: CVE-2026-31809, GHSA-pmc9-f5qr-2pcr
Record: https://patchnext.com/advisories/cve-2026-31809 (revision 1, source checked 26 Oct 2026, 15:15 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.4)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/siyuan-note/siyuan/kernel 0.0.0-20260310025236-297bd526708f. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/siyuan-note/siyuan/kernel: affected < 0.0.0-20260310025236-297bd526708f; fixed in 0.0.0-20260310025236-297bd526708f

## Suggested inspection (read-only)
- Go github.com/siyuan-note/siyuan/kernel: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/siyuan-note/siyuan/kernel.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-pmc9-f5qr-2pcr (GitHub-reviewed advisory GHSA-pmc9-f5qr-2pcr lists affected ranges: Go github.com/siyuan-note/siyuan/kernel >=0 <0.0.0-20260310025236-297bd526708f)

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