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SiYuan before v3.8.4 Authentication Bypass via Missing Origin Header

Type: advisorySource: Official CVE List1 source record

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.

Announced Source revision 1
Original source ↗

CVE-2026-100646

Primary source · Revision 1

Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.

Security context

Source reference: cve:CVE-2026-100646

siyuan

Source reference: /containers/cna/affected/0/product

Affected versions
Not stated in this record
Fixed versions
Not stated in this record
Prerequisites
Not stated in this record

Structured affected-version data

Original package identities and version rules from this source.

[
  {
    "vendor": "siyuan-note",
    "product": "siyuan",
    "versions": [
      {
        "status": "affected",
        "version": "0",
        "lessThan": "3.8.4",
        "versionType": "semver"
      },
      {
        "status": "unaffected",
        "version": "3.8.4",
        "versionType": "semver"
      }
    ],
    "packageURL": "pkg:golang/github.com/siyuan-note/siyuan",
    "defaultStatus": "unaffected"
  }
]
Related CVEs
CVE-2026-100646

Source reference: /cveMetadata/cveId

Publisher severity

high

Source reference: /containers/cna/metrics

Event
#4420 · Revision 1
Added to Heist Feed
Publisher date
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