CVE-2026-100646: Origin Validation Error in siyuan-note siyuan
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.
AI Analysis
Technical Summary
SiYuan versions up to 3.8.3 contain an origin validation error in the kernel's authentication guards (CheckAuth and IsSessionOriginAllowed). These checks incorrectly allow requests without an HTTP Origin header, assuming all browser-initiated cross-site requests include one. However, browsers omit the Origin header on cross-site top-level GET navigations and no-cors GET subresource loads. Given the session cookie is SameSite=Lax, a single cross-site GET request from an attacker-controlled page can be granted RoleAdministrator. Additionally, content-type sniffing on the /api/network/proxy endpoint allows attacker-controlled HTML to be served under SiYuan's origin (http://127.0.0.1:6806), enabling script execution, administrator API invocation, and exfiltration of the kernel API token. This vulnerability is resolved in SiYuan version 3.8.4.
Potential Impact
An unauthenticated remote attacker can exploit this vulnerability to gain administrator privileges via cross-site GET requests. This enables arbitrary script execution within the SiYuan origin, invocation of administrator APIs, and exfiltration of persistent kernel API tokens. The impact includes full administrative control over the affected SiYuan instance, potentially compromising all stored data and system integrity.
Mitigation Recommendations
This vulnerability is fixed in SiYuan version 3.8.4. Users should upgrade to version 3.8.4 or later to remediate this issue. No additional mitigation actions are required beyond applying the official fix.
CVE-2026-100646: Origin Validation Error in siyuan-note siyuan
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.
CVSS v4.0
Score 8.6high
Affected software
siyuan-note
siyuan
pkg:github/siyuan-note/siyuanRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
SiYuan versions up to 3.8.3 contain an origin validation error in the kernel's authentication guards (CheckAuth and IsSessionOriginAllowed). These checks incorrectly allow requests without an HTTP Origin header, assuming all browser-initiated cross-site requests include one. However, browsers omit the Origin header on cross-site top-level GET navigations and no-cors GET subresource loads. Given the session cookie is SameSite=Lax, a single cross-site GET request from an attacker-controlled page can be granted RoleAdministrator. Additionally, content-type sniffing on the /api/network/proxy endpoint allows attacker-controlled HTML to be served under SiYuan's origin (http://127.0.0.1:6806), enabling script execution, administrator API invocation, and exfiltration of the kernel API token. This vulnerability is resolved in SiYuan version 3.8.4.
Potential Impact
An unauthenticated remote attacker can exploit this vulnerability to gain administrator privileges via cross-site GET requests. This enables arbitrary script execution within the SiYuan origin, invocation of administrator APIs, and exfiltration of persistent kernel API tokens. The impact includes full administrative control over the affected SiYuan instance, potentially compromising all stored data and system integrity.
Mitigation Recommendations
This vulnerability is fixed in SiYuan version 3.8.4. Users should upgrade to version 3.8.4 or later to remediate this issue. No additional mitigation actions are required beyond applying the official fix.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- VulnCheck
- Date Reserved
- 2026-09-26T02:33:07.898Z
- Cvss Version
- 4.0
- State
- PUBLISHED
Threat ID: 6ab7c9a7f7a7c5410652fd2e
Added to database: 09/26/2026, 13:33:27 UTC
Last enriched: 09/26/2026, 14:03:07 UTC
Last updated: 09/27/2026, 03:21:36 UTC
Views: 12
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