SiYuan: Localhost-trust admin bypass on auth-code-gated endpoints, with potential remote reachability via the fixed-port proxy

Exploitation

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

CVSS

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

EPSS

• CVE-2026-72809: 0.30% estimated exploitation activity in the next 30 days; percentile 22.77 (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.

CVE: This vulnerability corresponds to CVE-2026-72809. Summary The kernel's CheckAuth grants RoleAdministrator to any request whose RemoteAddr is loopback (127.0.0.1), for a specific set of endpoints, and these localhost bypasses sit outside the accessAuthCode gate so they apply even when an access auth code is configured. This is demonstrated live (Part A below). Separately, the fixed-port reverse proxy (fixedport.go) forwards requests to the kernel over loopback and injects no authentication token, and no SetTrustedProxies is configured, so gin does not derive the client address from forwarding headers. By code inspection, a request forwarded through this proxy would reach the kernel with RemoteAddr = 127.0.0.1. If the fixed-port proxy is bound to a network interface (via NetworkServe) and forwards remote requests to the kernel this way, the localhost bypass would grant a remote unauthenticated caller admin on those endpoints. This second step is established by reading the code but…

Published by the source

3 Sep 2026, 22:34 UTC

Last modified by the source

10 Sep 2026, 15:15 UTC

Source last checked

26 Oct 2026, 15:29 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-3mp7-4rh5-jrv9

2. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GO-2026-6386

3. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-3mp7-4rh5-jrv9

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# Patch Next advisory brief: CVE-2026-72809

Advisory: SiYuan: Localhost-trust admin bypass on auth-code-gated endpoints, with potential remote reachability via the fixed-port proxy
IDs: CVE-2026-72809, GHSA-3mp7-4rh5-jrv9
Record: https://patchnext.com/advisories/cve-2026-72809 (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 8.0)
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 0.0.0-20260723031701-9c16e9851f0b. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/siyuan-note/siyuan/kernel: affected < 0.0.0-20260723031701-9c16e9851f0b; fixed in 0.0.0-20260723031701-9c16e9851f0b

## 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-3mp7-4rh5-jrv9 (OSV record GHSA-3mp7-4rh5-jrv9 lists affected ranges: Go github.com/siyuan-note/siyuan/kernel >=0 <0.0.0-20260723031701-9c16e9851f0b (fixed))
- Verified: https://osv.dev/vulnerability/GO-2026-6386 (OSV record GO-2026-6386 lists affected ranges: Go github.com/siyuan-note/siyuan/kernel >=0 <0.0.0-20260723031701-9c16e9851f0b (fixed))
- Verified: https://github.com/advisories/GHSA-3mp7-4rh5-jrv9 (GitHub-reviewed advisory GHSA-3mp7-4rh5-jrv9 lists affected ranges: Go github.com/siyuan-note/siyuan/kernel >=0 <0.0.0-20260723031701-9c16e9851f0b)

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