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.

Scoring

Severity
MEDIUM
CVSS base score
6.9
CVSS vector
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
EPSS probability
0.24%
CWE
CWE-201
Published
2026-08-22
Last modified
2026-08-26

Affected products

Weakness type

Related vulnerabilities

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