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.
{
"cna_assigner": "VulnCheck",
"cwe_ids": [
"CWE-201"
],
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/59xxx/CVE-2026-59809.json"
}{
"extracted_events": [
{
"introduced": "0"
},
{
"fixed": "3.8.0"
},
{
"fixed": "v3.8.0"
}
],
"source": [
"AFFECTED_FIELD",
"DESCRIPTION"
]
}