The SSRF vulnerability in SiYuan before version 3.7.4 arises from the isPrivateIP function in kernel/util/net.go, which is used by SSRFSafeDialer to enforce SSRF protection in SafeMode. The function only checks for loopback, link-local unicast, private, and unspecified IP addresses but does not recognize IPv6 transition addresses such as NAT64 (64:ff9b::/96), 6to4 (2002::/16), and Teredo (2001::/32) that embed private IPv4 addresses. An authenticated attacker can exploit this by supplying URLs resolving to these transition addresses via proxy endpoints, bypassing SSRF protections and accessing internal services including cloud metadata endpoints like 169.254.169.254. The forward proxy returns the full response body, enabling full-read SSRF attacks that can lead to credential theft and internal network reconnaissance.

An authenticated attacker can bypass SSRF protections in SiYuan before v3.7.4 when SafeMode is enabled, allowing them to access internal services and cloud metadata endpoints. This can lead to theft of instance credentials and internal port scanning, potentially compromising internal infrastructure confidentiality and security.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is available, avoid enabling SafeMode or restrict access to proxy endpoints to trusted users only. Monitor for vendor updates regarding a patch or official remediation.