Vulnerability in Siyuan-Note Siyuan
CVE-2026-59809
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 4.9 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:N.
EPSS exploit prediction
EPSS: 0.004 (33.3th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 33rd percentile — 33.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.004 · change: +0.002
Affected products
Weakness classification (CWE)
References
- github.com/siyuan-note/siyuan/security/advisories/GHSA-853m-gvvm-6rvx (vendor-advisory)
- www.vulncheck.com/advisories/siyuan-before-secret-exfiltration-via-http-request… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-59809?
- CVE-2026-59809 is a medium-severity vulnerability in Siyuan-Note Siyuan, classified under Insertion of Sensitive Information into Sent Data. CVSS score: 4.9/10. Published 2026-08-22.
- How severe is CVE-2026-59809?
- Medium severity. CVSS v3 base score is 4.9 out of 10.