Vulnerability · Published Aug 18, 2026 · Assigned by VulnCheck
CVE-2026-74905SiYuan before v3.7.4 SSRF via IPv6 Transition Address Bypass
High 7.1
In plain English
A high-severity server-side request forgery in siyuan from siyuan-note. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 33% of all known vulnerabilities).
Official 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.
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| siyuan-note | siyuan | 0 – before 3.7.4 |
Weakness: CWE-918 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N
References
- GitHub Security Advisory (GHSA-qq8m-8p8v-x4xg) vendor-advisory
- VulnCheck Advisory: SiYuan before v3.7.4 SSRF via IPv6 Transition Address Bypass third-party-advisory