# CVE-2026-59809: SiYuan before v3.8.0 Secret Exfiltration via http_request URL

> Attackers can exfiltrate stored secrets by crafting malicious URLs in the http_request MCP tool, exposing sensitive data to external hosts.

- **Severity:** Medium 6.9 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:N/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:** 22 Aug 2026
- **Updated:** 26 Aug 2026
- **Also known as:** GHSA-27jw-6xjf-hgxj, GHSA-853m-gvvm-6rvx

## What is CVE-2026-59809?

CVE-2026-59809 is a medium-severity vulnerability in siyuan-note siyuan, published on 22 Aug 2026. An attacker needs administrator access to exploit it, with no action from the victim.

### Official description

SiYuan before v3.8.0 interpolates secret placeholders into the destination URL parameter of the http_request MCP tool, allowing attackers to exfiltrate stored secrets. An MCP client can craft a request with an attacker-controlled URL containing secret placeholders to send plaintext secret values to any public host without confirmation.

Weakness: CWE-201 (Insertion of Sensitive Information Into Sent Data)

## Which versions are affected by CVE-2026-59809?


## How do I fix CVE-2026-59809?

No fix has been published for CVE-2026-59809 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-59809 being exploited?

There is no known exploitation of CVE-2026-59809 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-59809 and fix it if it is affected.

What it is: CVE-2026-59809 is a medium-severity vulnerability in siyuan-note siyuan, published on 22 Aug 2026. An attacker needs administrator access to exploit it, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-59809 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-2026-59809/ (Markdown: https://insights.sbomify.com/CVE-2026-59809/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-59809
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-59809
- OSV: https://osv.dev/vulnerability/CVE-2026-59809

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-59809/
Summaries are generated and may contain mistakes; the official description above is the record.