# CVE-2026-100633: SiYuan 3.8.0 through 3.8.3 Path Traversal via MCP File Operations

> Authenticated administrators can bypass sensitive-path guards in MCP file operations to read or overwrite protected configuration and key files.

- **Severity:** High 8.5 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 26 Sep 2026
- **Updated:** 5 Oct 2026
- **Also known as:** GHSA-9g6v-r3xf-673q, GHSA-x2gq-fcjj-cxqr

## What is CVE-2026-100633?

CVE-2026-100633 is a high-severity path traversal vulnerability in siyuan-note siyuan, published on 26 Sep 2026. An attacker needs administrator access to exploit it, with no action from the victim.

### Official 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.

Weakness: CWE-863 (Incorrect Authorization)

## Which versions are affected by CVE-2026-100633?


## How do I fix CVE-2026-100633?

No fix has been published for CVE-2026-100633 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-100633 being exploited?

There is no known exploitation of CVE-2026-100633 in the wild and no public exploit code.

Public exploit code:

- Published SiYuan CVE · Reporter: dpfkdlemtp · Official record and advisory links (github_poc): https://github.com/dpfkdlemtp/CVE-2026-100633

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-100633 and fix it if it is affected.

What it is: CVE-2026-100633 is a high-severity path traversal vulnerability in siyuan-note siyuan, published on 26 Sep 2026. An attacker needs administrator access to exploit it, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-100633 in the wild and no public exploit code.

Affected product: siyuan-note siyuan. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-100633/ (Markdown: https://insights.sbomify.com/CVE-2026-100633/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-100633
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-100633
- OSV: https://osv.dev/vulnerability/CVE-2026-100633

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-100633/
Summaries are generated and may contain mistakes; the official description above is the record.