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SiYuan EUVDEUVD-2026-70410

| CVE-2026-85175 HIGH
Files or Directories Accessible to External Parties (CWE-552)
2026-09-03 VulnCheck GHSA-gg9w-4vv2-vjcm
8.7
CVSS 4.0 · Vendor: VulnCheck
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Severity by source

Vendor (VulnCheck) PRIMARY
8.7 HIGH
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
vuln.today AI
8.1 HIGH

Network-accessible POST endpoint; low privilege (any authenticated user, effectively none on default no-auth instances); C:H for key disclosure, I:H for CA forgery; A:N as no availability impact mechanism is described.

3.1 AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
4.0 AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

Primary rating from Vendor (VulnCheck).

CVSS VectorVendor: VulnCheck

Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
X

Lifecycle Timeline

4
POC Analysis Generated
Sep 07, 2026 - 23:33 vuln.today
Patch available
Sep 03, 2026 - 13:01 EUVD
Analysis Generated
Sep 03, 2026 - 11:52 vuln.today
CVE Published
Sep 03, 2026 - 11:22 cve.org
HIGH 8.7

DescriptionCVE.org

SiYuan versions <= 3.8.1 (fixed in v3.8.2) contain an incomplete blocklist in the IsForbiddenAbsPath() function (kernel/util/path_guard.go), which only blocks conf/conf.json by exact match and does not restrict the TLS private key (conf/key.pem) or CA private key (conf/ca.key) stored in the same conf/ directory. Because the getFile handler skips the blocklist for RoleAdministrator and all authenticated users receive RoleAdministrator in v3.8.1, any user (or any client on a default no-auth-code instance) can retrieve these private keys via POST /api/file/getFile. On deployments with TLS enabled, this allows decryption of captured HTTPS traffic (key.pem) and forging of certificates trusted by clients that imported SiYuan's CA (ca.key).

AnalysisAI

TLS private key disclosure in SiYuan <=3.8.1 allows any authenticated user - or any network client on default no-auth-code deployments - to exfiltrate the server's TLS private key (conf/key.pem) and CA private key (conf/ca.key) via a simple POST to /api/file/getFile. The root cause is a dual flaw: the IsForbiddenAbsPath() blocklist covers only conf/conf.json by exact match while leaving sibling key material unprotected, and the getFile handler unconditionally skips the blocklist for RoleAdministrator - a role granted to every authenticated user in v3.8.1. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

Access
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Delivery
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Exploit
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Execution
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Persist
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Impact
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Vulnerability AssessmentAI

Exploitation Network access to the SiYuan HTTP/HTTPS API port is required. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment The vendor-assigned CVSS 4.0 score of 8.7 (AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H) is largely defensible, with one notable concern: the VA:H (high availability impact on the vulnerable system) component is not directly supported by the description, which identifies no mechanism for service disruption - key compromise forces operational key rotation and certificate revocation, but that is an administrative consequence rather than an availability impact caused by the exploit itself. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario Full exploit scenario with step-by-step reproduction available after sign-in.
Remediation The primary fix is upgrading to SiYuan v3.8.2, which corrects the incomplete blocklist in IsForbiddenAbsPath() to include conf/key.pem and conf/ca.key, per GitHub Security Advisory GHSA-4wwp-f6gw-6qm5 (https://github.com/siyuan-note/siyuan/security/advisories/GHSA-4wwp-f6gw-6qm5). … Detailed patch versions, workarounds, and compensating controls in full report.

Recommended ActionAI

Within 24 hours, inventory all SiYuan deployments running version 3.8.1 or earlier and assess network exposure, prioritizing TLS-enabled instances; implement network-level access restrictions (VPN, IP allowlisting) for critical deployments if immediate patching is not feasible. …

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EUVD-2026-70410 vulnerability details – vuln.today

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