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

Severity: medium (CVSS 4.9 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-08-22 · updated 2026-10-12
Weakness: CWE-201

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: before 3.8.0 — fixed in 3.8.0

How to fix

Upgrade to a fixed version: siyuan-note siyuan 3.8.0. Check the vendor advisory for mitigations.

References

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

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