CVE-2026-72809 PUBLISHED

SiYuan before v3.7.4 Authentication Bypass via Localhost Trust

Assigner: VulnCheck
Reserved: 10.08.2026 Published: 12.08.2026 Updated: 12.08.2026

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.

Metrics

CVSS Vector: 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
CVSS Score: 7.1

Product Status

Vendor siyuan-note
Product siyuan
Versions Default: unaffected
  • affected from 0 to 3.7.4 (excl.)
  • Version 3.7.4 is unaffected

Credits

  • Shirshakhtml reporter

References

Problem Types

  • Authentication Bypass by Spoofing CWE