CVE-2026-74905Public exploitNetwork attack vector

Internal response disclosure via IPv6 SSRF bypass

Published Aug 18, 2026 · Updated Aug 19, 2026

Server-side request forgery in SiYuan before 3.7.4 lets attackers read internal HTTP responses through the application's proxy endpoints. The isPrivateIP check in kernel/util/net.go relies on Go address classifiers that do not treat NAT64, 6to4, and Teredo transition prefixes as private, so SSRFSafeDialer accepts hostnames that resolve to embedded private or metadata IPv4 targets. When SafeMode is enabled and the forward, WebSocket, SSE, or plugin proxy paths are reachable, the flaw becomes a full-read SSRF that can expose cloud instance credentials, internal services, and network topology.

CVSS severity7.1
High
EPSS probability0.32%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Server-side request forgery in SiYuan before 3.7.4 lets attackers read internal HTTP responses through the application's proxy endpoints. The isPrivateIP check in kernel/util/net.go relies on Go address classifiers that do not treat NAT64, 6to4, and Teredo transition prefixes as private, so SSRFSafeDialer accepts hostnames that resolve to embedded private or metadata IPv4 targets. When SafeMode is enabled and the forward, WebSocket, SSE, or plugin proxy paths are reachable, the flaw becomes a full-read SSRF that can expose cloud instance credentials, internal services, and network topology.

The record

CVE
CVE-2026-74905
Published
Aug 18, 2026
Updated
Aug 19, 2026
Vendor
SiYuan Note
Product
SiYuan
Classifications
CWE-918, T1190
Attack vector
network
Privileges
Unavailable

Timeline

How it unfolded

  1. Aug 18, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 19, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <3.7.4

What conditions does exploitation require?

Attack vectornetwork
Required privilegesUnavailable in this record.

What is affected?

SiYuan Note · SiYuanversion=0 <3.7.4

Published CVSS scores

7.1VulnCheckCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N
6.9VulnCheckCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:L/SI:L/SA:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-918Server-Side Request Forgery (SSRF)
T1190Exploit Public-Facing Application

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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