CVE-2026-74905: Server-Side Request Forgery (SSRF) in siyuan-note siyuan
SiYuan note-taking software versions before 3.7.4 contain a server-side request forgery (SSRF) vulnerability in the isPrivateIP function. This function fails to recognize certain IPv6 transition addresses that embed private IPv4 destinations, allowing authenticated attackers to bypass SSRF protections in SafeMode. Exploitation can occur via network forward proxy, WebSocket proxy, or SSE proxy endpoints, enabling attackers to access internal services and cloud metadata endpoints such as 169.254.169.254. The vulnerability allows full-read SSRF, potentially leading to credential theft and internal network reconnaissance.
AI Analysis
Technical Summary
CVE-2026-74905 is an SSRF vulnerability in SiYuan note-taking software prior to version 3.7.4. The flaw exists in the isPrivateIP function within kernel/util/net.go, which is used by SSRFSafeDialer to enforce SSRF protection in SafeMode. The function checks for loopback, link-local unicast, private, and unspecified IP addresses but does not recognize IPv6 transition addresses (NAT64 64:ff9b::/96, 6to4 2002::/16, Teredo 2001::/32) that encapsulate private IPv4 addresses. This oversight allows an authenticated attacker to bypass SSRF protections by supplying URLs resolving to these transition addresses via proxy endpoints, enabling access to internal services and cloud metadata endpoints. The forward proxy returns full response bodies, making this a full-read SSRF vulnerability that can be exploited to steal instance credentials and perform internal port scanning.
Potential Impact
An authenticated attacker can bypass SSRF protections in SafeMode and access internal network services and cloud metadata endpoints. This can lead to theft of instance credentials, unauthorized access to internal services, and reconnaissance of internal infrastructure. The vulnerability is rated medium severity with a CVSS 4.0 score of 6.9.
Mitigation Recommendations
A fix is available in SiYuan version 3.7.4. Users should upgrade to version 3.7.4 or later to remediate this SSRF vulnerability. Until upgraded, avoid enabling SafeMode or restrict access to proxy endpoints to trusted users only.
CVE-2026-74905: Server-Side Request Forgery (SSRF) in siyuan-note siyuan
Description
SiYuan note-taking software versions before 3.7.4 contain a server-side request forgery (SSRF) vulnerability in the isPrivateIP function. This function fails to recognize certain IPv6 transition addresses that embed private IPv4 destinations, allowing authenticated attackers to bypass SSRF protections in SafeMode. Exploitation can occur via network forward proxy, WebSocket proxy, or SSE proxy endpoints, enabling attackers to access internal services and cloud metadata endpoints such as 169.254.169.254. The vulnerability allows full-read SSRF, potentially leading to credential theft and internal network reconnaissance.
CVSS v4.0
Score 6.9medium
Affected software
siyuan-note
siyuan
pkg:github/siyuan-note/siyuanRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-74905 is an SSRF vulnerability in SiYuan note-taking software prior to version 3.7.4. The flaw exists in the isPrivateIP function within kernel/util/net.go, which is used by SSRFSafeDialer to enforce SSRF protection in SafeMode. The function checks for loopback, link-local unicast, private, and unspecified IP addresses but does not recognize IPv6 transition addresses (NAT64 64:ff9b::/96, 6to4 2002::/16, Teredo 2001::/32) that encapsulate private IPv4 addresses. This oversight allows an authenticated attacker to bypass SSRF protections by supplying URLs resolving to these transition addresses via proxy endpoints, enabling access to internal services and cloud metadata endpoints. The forward proxy returns full response bodies, making this a full-read SSRF vulnerability that can be exploited to steal instance credentials and perform internal port scanning.
Potential Impact
An authenticated attacker can bypass SSRF protections in SafeMode and access internal network services and cloud metadata endpoints. This can lead to theft of instance credentials, unauthorized access to internal services, and reconnaissance of internal infrastructure. The vulnerability is rated medium severity with a CVSS 4.0 score of 6.9.
Mitigation Recommendations
A fix is available in SiYuan version 3.7.4. Users should upgrade to version 3.7.4 or later to remediate this SSRF vulnerability. Until upgraded, avoid enabling SafeMode or restrict access to proxy endpoints to trusted users only.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- VulnCheck
- Date Reserved
- 2026-08-17T10:48:45.738Z
- Cvss Version
- 4.0
- State
- PUBLISHED
Threat ID: 6a844364c6e8be03322294a4
Added to database: 08/18/2026, 11:35:00 UTC
Last enriched: 09/11/2026, 23:18:33 UTC
Last updated: 10/02/2026, 02:46:06 UTC
Views: 61
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