Is CVE-2026-59809 being exploited?

No public exploit is currently tracked.

How severe is CVE-2026-59809?

CVE-2026-59809 has a CVSS v3 severity of MEDIUM (4.9).

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CVE-2026-59809

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.