SiYuan: Stored and reflected XSS in SiYuan through an SVG sanitizer bypass

Exploitation

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

CVSS

8.7 · CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N

EPSS

• CVE-2026-66394: 0.34% estimated exploitation activity in the next 30 days; percentile 27.13 (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.

Summary SiYuan cleans user supplied SVG with util.SanitizeSVG before it serves the file inline as image/svg+xml. This cleaner is the guard behind the Editor.AllowSVGScript setting, which is off by default, so a <script inside an SVG is meant to be removed. The cleaner reads the input as HTML, but the browser reads the served file as XML (SVG). Because the two parsers treat some tags differently, a <script can be hidden so the cleaner never removes it. The cleaned file still holds a working script. When a browser opens that file as an SVG document, the script runs in the app origin. There is no Content Security Policy in the product to stop it. The same bug can be reached in two ways. Both share one root cause (the cleaner), so one fix in the cleaner closes both: Reflected, through a single link: GET /api/icon/getDynamicIcon Stored, through a planted .svg asset: GET /assets/<name.svg I confirmed this on a live SiYuan 3.7.2 kernel. Root cause util.SanitizeSVG (kernel/util/misc.go:319)…

Published by the source

3 Sep 2026, 14:53 UTC

Last modified by the source

10 Sep 2026, 15:25 UTC

Source last checked

26 Oct 2026, 15:29 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-99rq-75j6-5j9f

2. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GO-2026-6364

3. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-99rq-75j6-5j9f

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# Patch Next advisory brief: CVE-2026-66394

Advisory: SiYuan: Stored and reflected XSS in SiYuan through an SVG sanitizer bypass
IDs: CVE-2026-66394, GHSA-99rq-75j6-5j9f
Record: https://patchnext.com/advisories/cve-2026-66394 (revision 3, source checked 26 Oct 2026, 15:29 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.7)
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 0.0.0-20260714095344-f08dee71ba8e. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/siyuan-note/siyuan/kernel: affected < 0.0.0-20260714095344-f08dee71ba8e; fixed in 0.0.0-20260714095344-f08dee71ba8e

## 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://osv.dev/vulnerability/GHSA-99rq-75j6-5j9f (OSV record GHSA-99rq-75j6-5j9f lists affected ranges: Go github.com/siyuan-note/siyuan/kernel >=0 <0.0.0-20260714095344-f08dee71ba8e (fixed))
- Verified: https://osv.dev/vulnerability/GO-2026-6364 (OSV record GO-2026-6364 lists affected ranges: Go github.com/siyuan-note/siyuan/kernel >=0 <0.0.0-20260714095344-f08dee71ba8e (fixed))
- Verified: https://github.com/advisories/GHSA-99rq-75j6-5j9f (GitHub-reviewed advisory GHSA-99rq-75j6-5j9f lists affected ranges: Go github.com/siyuan-note/siyuan/kernel >=0 <0.0.0-20260714095344-f08dee71ba8e)

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