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CVE-2026-74905— SiYuan before v3.7.4 SSRF via IPv6 Transition Address Bypass

Quick assessment

Affected
siyuan-note siyuan
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

SiYuan是SiYuan团队开源的一款文档管理软件。 SiYuan 3.7.4之前版本存在服务端请求伪造漏洞，该漏洞源于isPrivateIP函数未识别IPv6转换地址，可能导致经过身份验证的攻击者通过代理端点绕过SSRF保护，访问内部服务和云元数据端点，窃取实例凭据或进行端口扫描。

CVSS 7.1 · High EPSS 0.35% · P27

Affected Version Matrix 2

VendorProduct Version RangeStatus
siyuan-note siyuan < 3.7.4 affected
3.7.4 unaffected
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I. Basic Information for CVE-2026-74905

Vulnerability Information
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Vulnerability Title
SiYuan before v3.7.4 SSRF via IPv6 Transition Address Bypass
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
服务端请求伪造(SSRF)
Source: CVE Program / CVE List V5
Vulnerability Title
SiYuan 服务端请求伪造漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
SiYuan是SiYuan团队开源的一款文档管理软件。 SiYuan 3.7.4之前版本存在服务端请求伪造漏洞，该漏洞源于isPrivateIP函数未识别IPv6转换地址，可能导致经过身份验证的攻击者通过代理端点绕过SSRF保护，访问内部服务和云元数据端点，窃取实例凭据或进行端口扫描。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
siyuan-note siyuan 0 ~ 3.7.4 -

II. Public POCs for CVE-2026-74905

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III. Intelligence Information for CVE-2026-74905

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Vendor Advisories for CVE-2026-74905 (1)

Other References for CVE-2026-74905 (1)

Same Patch Batch · siyuan-note · 2026-08-18 · 5 CVEs total

CVE-2026-74902 8.6 HIGH SiYuan before v3.7.4 XSS-to-RCE via malicious filename upload
CVE-2026-74906 7.5 HIGH SiYuan before v3.7.4 Incorrect Authorization via Publish Access
CVE-2026-74904 7.5 HIGH SiYuan before v3.7.4 Missing Authorization via block API
CVE-2026-74903 4.3 MEDIUM SiYuan before v3.7.4 Insufficient Access Control via spinBlockDOM

IV. Related Vulnerabilities

Same product: siyuan
Same vendor: siyuan-note
Same weakness: CWE-918

V. Comments for CVE-2026-74905

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