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CVE-2026-82234— SiYuan before v3.8.1 SSRF via DNS-Rebinding TOCTOU

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团队开源的一个以隐私为先的个人知识管理系统。 SiYuan 3.8.1之前版本存在服务端请求伪造漏洞，该漏洞源于http_request和web_fetch代理工具仅在防御时执行DNS解析而未验证连接时的解析结果，导致服务器端请求伪造，攻击者可通过DNS重绑定绕过SSRF防御，访问云实例元数据和内部服务。

CVSS 8.2 · High EPSS 0.36% · P28

Affected Version Matrix 2

VendorProduct Version RangeStatus
siyuan-note siyuan < 3.8.1 affected
3.8.1 unaffected
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I. Basic Information for CVE-2026-82234

Vulnerability Information
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Vulnerability Title
SiYuan before v3.8.1 SSRF via DNS-Rebinding TOCTOU
Source: CVE Program / CVE List V5
Vulnerability Description
SiYuan versions before v3.8.1 contain a server-side request forgery vulnerability in the http_request and web_fetch agent tools that perform DNS resolution only at guard time without validating the connect-time resolution. Attackers can use DNS rebinding to answer the guard resolution with a public IP and the connect resolution with a private or metadata IP, bypassing the SSRF defense to access cloud instance metadata and internal services.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/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团队开源的一个以隐私为先的个人知识管理系统。 SiYuan 3.8.1之前版本存在服务端请求伪造漏洞，该漏洞源于http_request和web_fetch代理工具仅在防御时执行DNS解析而未验证连接时的解析结果，导致服务器端请求伪造，攻击者可通过DNS重绑定绕过SSRF防御，访问云实例元数据和内部服务。
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 ~ 3.8.1 -

II. Public POCs for CVE-2026-82234

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III. Intelligence Information for CVE-2026-82234

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Vendor Advisories for CVE-2026-82234 (2)

IV. Related Vulnerabilities

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

V. Comments for CVE-2026-82234

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