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CVE-2026-85175

HIGH 8.7 PoC AVAILABLE

Published 2026-09-03 · Last modified 2026-09-03

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).

EXPLOIT AVAILABLE

Public exploit or PoC code exists. Modeled probability is still low, but the barrier to attack is reduced — watch closely.

Exploitation likelihood

0.2%chance of exploitation in 30 days · 8th percentile

○ In CISA KEV ● Public exploit / PoC

Impact if exploited

8.7CVSS 4.0 · HIGH

  • ConfidentialityHigh
  • IntegrityHigh
  • AvailabilityHigh

What an attacker needs

  • ✓Access: Reachable over the network — no local access needed
  • ⚠Privileges: Requires a low-privilege account
  • ✓User interaction: No user interaction needed
  • ✓Complexity: No special conditions — reliably repeatable
  • ✓Requirements: No special attack requirements

✓ lowers the bar for an attacker · ⚠ raises it

Proof of concept & exploit code

Test against your own equipment

curl -s https://vulnpedia.com/cve/CVE-2026-85175/poc.jsonMachine-readable PoC index for this CVE (for automation).

Listed for defensive triage, patch verification, and authorized testing on systems you own. Machine-readable: /cve/CVE-2026-85175/poc.json

Affected

Vendors Siyuan Note

Products Siyuan

Weakness (CWE)

  • CWE-552: Files or Directories Accessible to External Parties

CVSS vector

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

All CVSS metrics

  • HIGH 8.7 v4.0 · CNA Primary
    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
  • HIGH 8.8 v3.1 · CNA Primary
    CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
  • HIGH 8.7 v4.0 · NVD Secondary
    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
  • HIGH 8.8 v3.1 · NVD Primary
    CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

References

Exploits & PoC

Advisories

Sources: NVD · CVE.org · EPSS