CVE-2026-59809

SiYuan before v3.8.0 Secret Exfiltration via http_request URL

MEDIUM
4.9
CVSS Score
Published: August 22, 2026 at 12:26 PM UTC
Updated: October 12, 2026 at 04:10 PM UTC
2 products affected across 2 vendorsSiyuanSiyuan

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Severity
MEDIUM4.9
Exploit prediction
EPSS 0.4%
SSVC
No known exploit

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

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v < 3.8.0
Affected range stops below 3.8.0, so it looks safe — our inference, not a vendor statement
0 ≤ v < 3.8.00
Vendor states this is fixed in 3.8.0 (unaffected)

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

4.9MEDIUMVulnCheck
Attack Vector
NETWORK
Complexity
LOW
Privileges
HIGH
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
NONE
Availability
NONE
Vector?

Quick Info

StatusDEFERRED
CWE
CWE-201

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