CVE-2026-74905: siyuan-note siyuan Server-Side Request Forgery (SSRF)

Vulnerability summary

CVE-2026-74905 is a high (CVSS 7.1) Server-Side Request Forgery (SSRF) vulnerability in siyuan-note siyuan. EPSS estimates a 0.35% chance of exploitation in the next 30 days, higher than 27.3% of scored vulnerabilities.

Timeline

1. 18-08-2026
   PublishedVulnerability first disclosed.
2. 19-08-2026
   Last modifiedVulnerability information updated.

Description

SiYuan before v3.7.4 contains a server-side request forgery (SSRF) vulnerability in the isPrivateIP function in kernel/util/net.go, used by SSRFSafeDialer to enforce SSRF protection in SafeMode. The function only checks for loopback, link-local unicast, private, and unspecified addresses and does not recognize IPv6 transition addresses (NAT64 64:ff9b::/96, 6to4 2002::/16, Teredo 2001::/32) that embed private IPv4 destinations. When SafeMode is enabled, an authenticated attacker can bypass the SSRF guard via the network forward proxy, WebSocket proxy, or SSE proxy endpoints by supplying a URL whose hostname resolves to such a transition address, reaching internal services and cloud metadata endpoints (e.g., 169.254.169.254). Because the forward proxy returns the full response body, this is a full-read SSRF that can be used to steal instance credentials, reach internal services, and port-scan internal infrastructure.

• CWE-918Server-Side Request Forgery (SSRF)The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination.