CVE-2026-126393: SiYuan before 3.8.10 SSRF via Skill-Install Download Redirect and DNS Rebinding
SiYuan before 3.8.10 contains a server-side request forgery vulnerability in the skill-install download path because fetchBytes performs only a parse-time hostname check instead of using ssrfSafeClient. Attackers can supply a skill URL via the MCP skill install action that redirects or DNS-rebinds to loopback addresses, reaching internal services and metadata endpoints.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
SiYuanto a version that resolves this vulnerability.Fixed in 3.8.10
Event History
Frequently Asked Questions
Who can exploit this issue?
An attacker needs to be able to provide a skill URL through the MCP skill install action. No authentication privilege is identified in the supplied severity vector, but exploitation requires user interaction.
What can the vulnerable request reach?
A supplied skill URL can redirect or DNS-rebind to loopback addresses, allowing requests to internal services and metadata endpoints.
Are versions before 3.8.10 affected?
The issue affects SiYuan versions before 3.8.10. The provided data does not state whether any particular default deployment configuration exposes the MCP skill install action.