Vulnerability in Siyuan-Note Siyuan
CVE-2026-72809
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 8.0 (High). Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:H.
EPSS exploit prediction
EPSS: 0.003 (20.3th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 20th percentile — 20.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.003 · change: +0.001
Affected products
- Siyuan-Note Siyuan — versions 0, 3.7.4
Weakness classification (CWE)
References
- github.com/siyuan-note/siyuan/security/advisories/GHSA-3mp7-4rh5-jrv9 (vendor-advisory)
- www.vulncheck.com/advisories/siyuan-before-authentication-bypass-via-localhost-… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-72809?
- CVE-2026-72809 is a high-severity vulnerability in Siyuan-Note Siyuan, classified under Authentication Bypass by Spoofing. CVSS score: 8.0/10. Published 2026-08-12.
- How severe is CVE-2026-72809?
- High severity. CVSS v3 base score is 8.0 out of 10.