# CVE-2026-85580: SiYuan before v3.8.2 Path Guard Bypass via Case Mismatch

> Attackers can bypass path guards to read sensitive configuration files in SiYuan by exploiting case-sensitive filesystem matching.

- **Severity:** High 7.1 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 4 Sep 2026
- **Updated:** 4 Sep 2026
- **Also known as:** GHSA-gwmf-gvp9-fcc2, GHSA-mmgw-3mx9-cfwp

## What is CVE-2026-85580?

CVE-2026-85580 is a high-severity path traversal vulnerability in siyuan-note siyuan, published on 4 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

SiYuan versions before v3.8.2 contain a path guard bypass vulnerability in the MCP file-access handler that uses case-sensitive matching on Linux filesystems. Attackers can read the protected publishAccess.json file by requesting case-variant paths like PublishAccess.json to disclose sensitive publish-access configuration and metadata.

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

## Which versions are affected by CVE-2026-85580?


## How do I fix CVE-2026-85580?

No fix has been published for CVE-2026-85580 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-85580 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-85580 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-85580 and fix it if it is affected.

What it is: CVE-2026-85580 is a high-severity path traversal vulnerability in siyuan-note siyuan, published on 4 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-85580 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-2026-85580/ (Markdown: https://insights.sbomify.com/CVE-2026-85580/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-85580
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-85580
- OSV: https://osv.dev/vulnerability/CVE-2026-85580

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-85580/
Summaries are generated and may contain mistakes; the official description above is the record.