---
cve: "CVE-2026-72809"
severity: "HIGH"
cvss: 7.1
epss: "21%"
vendor: "siyuan-note"
kev: false
exploited: false
published: "2026-08-12 20:17:53"
tags: [cve, security, high]
source: tsecurity.de CVE-Dossier
exported: "2026-09-04T03:05:33+02:00"
---

# CVE-2026-72809

> 7.1 HIGH · 🧪 PoC

## Beschreibung

SiYuan versions <= v3.7.2 (patched in v3.7.4) contain an authentication bypass vulnerability in the kernel's CheckAuth function, which grants the administrator role (RoleAdministrator) to any request whose RemoteAddr is loopback (127.0.0.1) for a specific set of endpoints (including /api/system/exit, getNetwork, getWorkspaceInfo, /assets/*, and /export/*). These localhost bypasses sit outside the access auth code gate, so they apply even when an access auth code is configured. Because the fixed-port reverse proxy forwards requests to the kernel over loopback without injecting an authentication token and does not configure trusted proxies, a request forwarded through this proxy reaches the kernel with RemoteAddr = 127.0.0.1. If the fixed-port proxy is bound to a network interface, this could allow a remote unauthenticated attacker to obtain admin access on the affected endpoints; however, per the advisory this remote forwarding behavior was established only by code inspection and was not reproduced end-to-end.

## CVSS-Vektor

```
CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:H/VI:L/VA:H/SC:N/SI:N/SA:N
```

| Metrik | Wert | Bewertung |
|---|---|---|
| AV Angriffsvektor | Lokal | good |
| AC Komplexität | Gering | bad |
| PR Privilegien | Keine | bad |
| UI Interaktion | Keine | bad |

## Referenzen

- <https://github.com/siyuan-note/siyuan/security/advisories/GHSA-3mp7-4rh5-jrv9>
- <https://www.vulncheck.com/advisories/siyuan-before-authentication-bypass-via-localhost-trust>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-72809) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_