CVE-2026-59809Public exploitNetwork attack vector

Secret exfiltration via destination URL interpolation

Published Aug 22, 2026 · Updated Aug 22, 2026

Secret exposure in SiYuan before 3.8.0 allows remote authenticated users to exfiltrate stored secrets through an MCP HTTP request. The http_request tool in kernel/mcp/tools/http_request.go passes its caller-controlled URL through ResolveSecretsVars, replacing secret placeholders with plaintext before sending the request. An MCP client able to invoke the tool can place a vault-secret placeholder in a public-host URL; GET requests send the value without confirmation, exposing stored API keys or other vault entries.

CVSS severity6.9
Medium
EPSS probability0.24%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Secret exposure in SiYuan before 3.8.0 allows remote authenticated users to exfiltrate stored secrets through an MCP HTTP request. The http_request tool in kernel/mcp/tools/http_request.go passes its caller-controlled URL through ResolveSecretsVars, replacing secret placeholders with plaintext before sending the request. An MCP client able to invoke the tool can place a vault-secret placeholder in a public-host URL; GET requests send the value without confirmation, exposing stored API keys or other vault entries.

The record

CVE
CVE-2026-59809
Published
Aug 22, 2026
Updated
Aug 22, 2026
Vendor
SiYuan Note
Product
SiYuan
Classifications
CWE-918, CWE-201
Attack vector
network
Privileges
admin

Timeline

How it unfolded

  1. Aug 22, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 22, 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 <3.8.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesadmin

What is affected?

SiYuan Note · SiYuanversion=0 <3.8.0

Published CVSS scores

6.9VulnCheckCVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N
4.9VulnCheckCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:N

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
Privilegesadmin
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-918Server-Side Request Forgery (SSRF)
CWE-201Insertion of Sensitive Information Into Sent Data

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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