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CVE-2026-74905

SiYuan before v3.7.4 SSRF via IPv6 Transition Address Bypass

HIGH
7.1
CVSS Score
Published: August 18, 2026 at 11:19 AM UTC
Updated: October 22, 2026 at 10:10 PM UTC
2 products affected across 2 vendorsSiyuanSiyuan

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Severity
HIGH7.1
Exploit prediction
EPSS 0.4%
SSVC
PoC

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

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

Siyuan· B3LOG
95%
v < 3.7.4
Affected range stops below 3.7.4, so it looks safe — our inference, not a vendor statement
Siyuan· Siyuan Notego
90%
0 ≤ v < 3.7.40
Vendor states this is fixed in 3.7.4 (unaffected)

Remediation

No guide yet

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

Patch and advisory references

References (2)

Vendor Advisory
Source: cverecord
https://github.com/siyuan-note/siyuan/security/advisories/GHSA-qq8m-8p8v-x4xg
Third Party Advisory
Source: cverecord
https://www.vulncheck.com/advisories/siyuan-before-ssrf-via-ipv6-transition-address-bypass

SSVC — Action Prioritization

SSVCPoCNot automatablePartial impact

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

CVSS

7.1HIGHVulnCheck
Attack Vector
NETWORK
Complexity
LOW
Privileges
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
LOW
Availability
NONE
Vector?

Quick Info

StatusDEFERRED
CWE
CWE-918

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