SiYuan EUVD-2026-112386

Requires a Windows deployment of SiYuan (the \\?\GLOBALROOT\Device\HarddiskVolumeN device-namespace alias is a Windows-only construct) running the kernel in server mode so that data/assets/ is served over HTTP. The attacker must be able to invoke POST /api/import/importStdMd - which in the published reproduction required the instance's API token for access - and must supply a GLOBALROOT-prefixed path (\\?\GLOBALROOT\..., \\.\GLOBALROOT\..., or the //?/ forward-slash form) targeting the workspace conf. Limiting factors: Windows-only applicability; affected versions 3.8.7 through 3.8.8 (the v3.8.7 resolveNamespaceAlias fix is incomplete); and the per-machine HarddiskVolumeN index must be discovered, though this is trivially enumerable (single-byte, ~1..6) and needs no prior knowledge. No non-default configuration beyond running the served kernel is required.

Signals are moderate and partly conflicting. The input scores this CVSS:4.0 AV:N/AC:L/AT:P/PR:H → 5.9 (Medium), while the vendor GHSA advisory scores the identical end-to-end chain CVSS:3.1 AV:N/AC:L/PR:N/UI:N/C:H/I:N/A:N → 7.5 (High); the disagreement is entirely in the privilege metric (PR:H vs PR:N), which must be resolved with the vendor before treating the raw number as authoritative. No EPSS probability and no KEV status are present in the input, and this CVE is NOT listed in CISA KEV, so there is no evidence of active or widespread exploitation. However, a detailed, dynamically-verified reproduction (real Windows 10, v3.8.7-beta.3) is published in the GHSA advisory, so the technical barrier to exploitation is low for anyone who can reach the import API. The vuln.today decision label is 'this_month' (schedule a fix within the month - not act_now/emergency), which fits the profile: real and verified, but gated by Windows-only applicability and the need to invoke an authenticated import endpoint rather than being mass-exploitable against default internet-facing deployments. Net: a genuine confidentiality issue worth patching on a normal cycle, not a drop-everything emergency, with the caveat that the CVSS numbers themselves conflict and should be verified with the vendor.

On a Windows SiYuan instance running in server/kernel mode, a caller able to reach the import API submits POST /api/import/importStdMd with a localPath of the form \\?\GLOBALROOT\Device\HarddiskVolumeN\...\<workspace>\conf, which survives the resolveNamespaceAlias normalization and bypasses the IsSensitivePath denylist. The API copies the workspace conf.json (containing the API token) and the TLS private key (ca-*.key) into data/assets/, which the kernel serves unauthenticated, so the attacker reads them back via GET /assets/. A working end-to-end reproduction is published in the GHSA advisory (verified on v3.8.7-beta.3, Windows 10 22H2).