CVE-2026-100646 Details
Description
SiYuan is a self-hosted personal knowledge management system. In versions up to and including 3.8.3, the kernel's authentication guards (CheckAuth in kernel/model/session.go and IsSessionOriginAllowed in kernel/util/net.go) fail open when the HTTP Origin header is absent, on the incorrect assumption that any browser-initiated cross-site request carries an Origin. Because browsers omit Origin on cross-site top-level GET navigations and no-cors GET subresource loads — and the session cookie is SameSite=Lax — a single cross-site GET issued from any attacker-controlled web page is granted RoleAdministrator, both on default installations with no access-authorization code and on password-protected instances with a live session. Combined with content-type sniffing on the /api/network/proxy endpoint, which allows attacker-controlled HTML to be served under SiYuan's own origin, this permits an unauthenticated remote attacker to execute arbitrary script in the SiYuan origin (http://127.0.0.1:6806), invoke administrator APIs, and exfiltrate the persistent kernel API token. This issue is fixed in version 3.8.4.
An authentication bypass vulnerability has been identified in SiYuan, a self-hosted personal knowledge management system, in versions prior to 3.8.4. The issue arises because the kernel's authentication checks fail to validate the HTTP Origin header correctly. This flaw allows an unauthenticated attacker to gain administrative privileges and access sensitive APIs. The vulnerability is exploited by sending a cross-site GET request from an attacker-controlled webpage, taking advantage of the absence of the Origin header, which browsers omit in certain cross-site navigation scenarios. This exploitation is further facilitated by content-type sniffing on the '/api/network/proxy' endpoint, enabling the execution of arbitrary scripts within the SiYuan application context.
Users can update to SiYuan version 3.8.4 or later, where this vulnerability has been fixed.
Metrics
CVSS 4.0 Severity and Vector Strings:
VolerionCVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
Volerion
Assessed Sep 26, 2026References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://github.com/siyuan-note/siyuan/security/advisories/GHSA-2w6q-wgc8-q743 | [email protected] | AdvisoryExploitRemedyVendor |
| https://www.vulncheck.com/advisories/siyuan-before-3.8.4-authentication-bypass-via-missing-origin-header | [email protected] | AdvisoryRemedy |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-346 | Origin Validation Error | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| SiYuan | <= 3.8.3 (semver) |
CPE
Remediation
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Change History
1 change record found show changes
| Date | Action | Recorded By |
|---|---|---|
| Sep 26, 2026 | New CVE Received | [email protected] |