SiYuan 3.8.0 through 3.8.3 Path Traversal via MCP File Operations (CVE-2026-100633) | HOL Guard CVE

High · CVSS 8.5CVE-2026-100633

SiYuan 3.8.0 through 3.8.3 Path Traversal via MCP File Operations

Answer in brief

CVE-2026-100633 records a High severity (CVSS 8.5) vulnerability in SiYuan 3.8.0 through 3.8.3 Path Traversal via MCP File Operations. The current sources do not mark it as known exploited. The current feed maps siyuan-note/siyuan (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Sep 26, 2026Updated Sep 26, 2026Source checked Sep 26, 2026First seen by HOL Sep 26, 2026Material review Sep 26, 2026

Upstream Advisory

Key facts

Risk: High · CVSS 8.5
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

CVSS is 8.5. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps siyuan-note/siyuan (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
siyuan-note/siyuangeneric	>=3.8.0 <3.8.4	3.8.4

Recommended response

Check inventory. Check lockfiles and deployed manifests for siyuan-note/siyuan.
Review the reported fix. Update siyuan-note/siyuan to 3.8.4 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Sep 26, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 26, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Sep 26, 2026

Sources and claim methodology

Upstream source description

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.

Quoted source text, attributed separately from HOL analysis.