# CVE-2026-59809

## Summary

- **CVE ID:** CVE-2026-59809
- **Severity:** MEDIUM
- **CVSS Score:** 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)
- **CWE:** CWE-201
- **Published:** Aug 22, 2026
- **Last Modified:** Aug 26, 2026

## 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.

## Affected Products

- siyuan-note — siyuan (0)
- siyuan-note — siyuan (3.8.0)

## References

- [CNA](https://github.com/siyuan-note/siyuan/security/advisories/GHSA-853m-gvvm-6rvx)
- [CNA](https://www.vulncheck.com/advisories/siyuan-before-secret-exfiltration-via-http-request-url)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.24%
- **EPSS Percentile:** 15.5

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-10._