CVE-2026-100633

MEDIUMPre-NVD 6.56.5—
EchelonGraph scoreHIGH confidence

Score 6.5 from GitHub Security Advisory (severity: HIGH) published 2026-09-26. A secondary CVSS source baseline 6.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
Trending — 3 sources updated this week
6.5EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.3%CVSS: 6.5Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

SiYuan is a self-hosted personal knowledge management system. In versions 3.8.0 through 3.8.3, the MCP file tool's sensitive-path guard (util.IsForbiddenAbsPath(), invoked from resolvePath()) is applied only to the allowed root of recursive operations and not to each resolved descendant path — an incomplete fix for GHSA-c8r8-95hg-mp34. An authenticated administrator using the in-app Agent or the external MCP server can therefore bypass the protected-workspace-file denylist: file.grep can return matching lines from non-hidden protected descendants (for example conf/conf.json, TLS keys, data/snippets/conf.json, data/templates/, data/.siyuan/publishAccess.json, notebook .siyuan internals, or the kernel log), file.copy can copy protected descendants to an ordinary path where file.read can then retrieve them, and unzip can overwrite protected descendants using ordinary, lexically contained ZIP member names. Because file.grep is globally classified as a safe action, it receives no per-call confirmation, and the confirmation cards for file.copy and unzip show only the allowed root arguments. This issue is fixed in version 3.8.4. Suggested title: SiYuan 3.8.0 through 3.8.3 Sensitive-Path Guard Bypass in Recursive MCP File Operations.

CVSS v3
6.5
EG Score
6.5MEDIUMhigh confidence
EG Risk
34
EG Risk 34/100CISA SSVC

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity65% × 45%
Exploitation0% × 40%
Automatability30% × 15%
CISA SSVC: Track at low or medium mission impact; Track or Attend at high (mission-essential systems).
Action: A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
EPSS PROB
0.3%
EPSS %ILE
23rd
KEV
Not listed

CISA SSVCTrack at low or medium mission impact; Track or Attend at high (mission-essential systems).

A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.

Exploitation none (no KEV listing, exploit record or EPSS ≥ 50%) · Automatable unknown (not published for this CVE) · Technical impact partial (CVSS below 9.0). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

September 26, 2026

Last Modified

September 26, 2026

Advisory Details (2)

Auto-updated Sep 26, 2026
🔬 Proof of concept available. Patch available. Sources: github.
generic Patch Available

SiYuan 3.8.0 through 3.8.3 Path Traversal via MCP File Operations | Advisories | VulnCheck

https://www.vulncheck.com/advisories/siyuan-3.8.0-through-3.8.3-path-traversal-via-mcp-file-operations
github Patch Available🟡 PoC Available

Incomplete fix for GHSA-c8r8-95hg-mp34: recursive MCP file operations bypass the sensitive-path guard · Advisory · siyuan-note/siyuan · GitHub

https://github.com/siyuan-note/siyuan/security/advisories/GHSA-9g6v-r3xf-673q

Vendor Advisories for CVE-2026-100633(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 19× in last 7d / 22× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-10-04 03:49 UTCEG score recompute
  2. 2026-10-04 03:49 UTCGHSA enrichment
  3. 2026-10-03 14:25 UTCEPSS rescore
  4. 2026-10-03 01:56 UTCEG score recompute
  5. 2026-10-03 01:56 UTCGHSA enrichment
  6. 2026-10-02 00:02 UTCEG score recompute
  7. 2026-10-02 00:02 UTCGHSA enrichment
  8. 2026-10-01 19:49 UTCEPSS rescore
  9. 2026-09-30 22:09 UTCEG score recompute
  10. 2026-09-30 22:09 UTCGHSA enrichment
  11. 2026-09-30 15:02 UTCEPSS rescore
  12. 2026-09-29 20:16 UTCEG score recompute
  13. 2026-09-29 20:16 UTCGHSA enrichment
  14. 2026-09-29 15:20 UTCEPSS rescore
  15. 2026-09-28 18:22 UTCEG score recompute
  16. 2026-09-28 18:22 UTCGHSA enrichment
  17. 2026-09-28 13:50 UTCEPSS rescore
  18. 2026-09-27 16:27 UTCEG score recompute
  19. 2026-09-27 16:27 UTCGHSA enrichment
  20. 2026-09-26 14:35 UTCEG score recompute
  21. 2026-09-26 13:39 UTCEG score recompute
  22. 2026-09-26 13:30 UTCMITRE cvelistV5first tracked

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Frequently asked(5)

What is CVE-2026-100633?
CVE-2026-100633 is a medium vulnerability published on September 26, 2026. SiYuan is a self-hosted personal knowledge management system. In versions 3.8.0 through 3.8.3, the MCP file tool's sensitive-path guard (util.IsForbiddenAbsPath(), invoked from resolvePath()) is applied only to the allowed root of recursive operations and not to each resolved descendant path — an…
When was CVE-2026-100633 disclosed?
CVE-2026-100633 was first published on September 26, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-100633 actively exploited?
CVE-2026-100633 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.3% probability of exploitation in the next 30 days (23rd percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-100633?
CVE-2026-100633 has a CVSS base score of 6.5 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-100633?
A fix for CVE-2026-100633 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-100633 are linked in the Vendor Advisories panel on this page.

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