{"id":"CVE-2026-72809","state":"PUBLISHED","title":"SiYuan before v3.7.4 Authentication Bypass via Localhost Trust","description":"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.","publishedAt":"2026-08-12T19:07:52.734Z","updatedAt":"2026-08-14T22:07:21.536Z","severity":{"score":7.1,"label":"High","version":"4.0","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","source":"VulnCheck"},"assigner":"VulnCheck","products":["siyuan-note siyuan"],"affected":[{"vendor":"siyuan-note","product":"siyuan","packageURL":"pkg:golang/github.com/siyuan-note/siyuan/kernel","defaultStatus":"unaffected","versions":[{"version":"0","status":"affected","lessThan":"3.7.4","versionType":"semver"},{"version":"3.7.4","status":"unaffected","versionType":"semver"}]}],"references":["https://github.com/siyuan-note/siyuan/security/advisories/GHSA-3mp7-4rh5-jrv9","https://www.vulncheck.com/advisories/siyuan-before-authentication-bypass-via-localhost-trust"],"weaknesses":["CWE-290"],"ingestedAt":"2026-10-29T20:12:58.252Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/72xxx/CVE-2026-72809.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-72809","state":"PUBLISHED","datePublished":"2026-08-12T19:07:52.734Z","dateUpdated":"2026-08-14T22:07:21.536Z","assignerShortName":"VulnCheck","assignerOrgId":"83251b91-4cc7-4094-a5c7-464a1b83ea10","dateReserved":"2026-08-10T15:11:49.794Z"},"containers":{"cna":{"title":"SiYuan before v3.7.4 Authentication Bypass via Localhost Trust","descriptions":[{"lang":"en","value":"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. 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