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CVE-2026-2859— Unauthenticated Host Enumeration via Observable Response Discrepancy on Deploy Agent Endpoint

Quick assessment

Affected
Checkmk GmbH Checkmk
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.

Checkmk是Checkmk公司的一个 IT 监控平台。 Checkmk 2.4.0p23之前版本、2.3.0p43之前版本和2.2.0版本存在安全漏洞，该漏洞源于权限执行不当，可能导致未经身份验证的用户通过观察deploy_agent端点不同的HTTP响应码来枚举现有主机，从而造成信息泄露。

AI Predicted 5.3 Difficulty: Easy EPSS 0.20% · P10

Possible ATT&CK Techniques 1 AI

T1083 · File and Directory Discovery
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I. Basic Information for CVE-2026-2859

Vulnerability Information
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Vulnerability Title
Unauthenticated Host Enumeration via Observable Response Discrepancy on Deploy Agent Endpoint
Source: CVE Program / CVE List V5
Vulnerability Description
Improper permission enforcement in Checkmk versions 2.4.0 before 2.4.0p23, 2.3.0 before 2.3.0p43, and 2.2.0 (EOL) allows unauthenticated users to enumerate existing hosts by observing different HTTP response codes in deploy_agent endpoint, which could lead to information disclosure.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
响应差异性信息暴露
Source: CVE Program / CVE List V5
Vulnerability Title
Checkmk 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Checkmk是Checkmk公司的一个 IT 监控平台。 Checkmk 2.4.0p23之前版本、2.3.0p43之前版本和2.2.0版本存在安全漏洞，该漏洞源于权限执行不当，可能导致未经身份验证的用户通过观察deploy_agent端点不同的HTTP响应码来枚举现有主机，从而造成信息泄露。
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
Checkmk GmbH Checkmk 2.4.0 ~ 2.4.0p23 -

II. Public POCs for CVE-2026-2859

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III. Intelligence Information for CVE-2026-2859

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Patches & Fixes for CVE-2026-2859 (1)

IV. Related Vulnerabilities

Same product: Checkmk
Same vendor: Checkmk GmbH
Same weakness: CWE-204