# CVE-2026-74798: SiYuan kernel Path Traversal via database_clean MCP tool

> An authenticated attacker can exploit a path traversal flaw in the MCP tool to read and delete arbitrary files on the host system.

- **Severity:** Critical 9.3 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:N/SC:H/SI:H/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:** 17 Aug 2026
- **Updated:** 18 Aug 2026
- **Also known as:** GHSA-mwfp-66vr-j373

## What is CVE-2026-74798?

CVE-2026-74798 is a critical path traversal vulnerability in siyuan-note siyuan, published on 17 Aug 2026. An attacker needs administrator access to exploit it, with no action from the victim.

### Official description

SiYuan kernel before v3.7.4 contains a path traversal vulnerability in the database_clean MCP tool. The tool performs only an empty-string check on the id parameter before passing it to RemoveUnusedAttributeView (kernel/model/attribute_view.go), which builds a filesystem path via filepath.Join without validating that id matches SiYuan's node-ID format. An authenticated MCP client can supply path traversal sequences in id to cause the kernel to copy an arbitrary file readable by the process into SiYuan's history directory (arbitrary file read) and then delete the original file (arbitrary file deletion). The corresponding HTTP API handler was hardened in GHSA-7hm9-v7vf-7g4w, but this MCP caller was not.

Weakness: CWE-22 (Improper Limitation of a Pathname to a Restricted Directory)

## Which versions are affected by CVE-2026-74798?


## How do I fix CVE-2026-74798?

No fix has been published for CVE-2026-74798 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-74798 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-74798 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-74798 and fix it if it is affected.

What it is: CVE-2026-74798 is a critical path traversal vulnerability in siyuan-note siyuan, published on 17 Aug 2026. An attacker needs administrator access to exploit it, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-74798 exists.

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-2026-74798/ (Markdown: https://insights.sbomify.com/CVE-2026-74798/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-74798
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-74798
- OSV: https://osv.dev/vulnerability/CVE-2026-74798

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-74798/
Summaries are generated and may contain mistakes; the official description above is the record.