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

Published Mar 13, 2026
·
Updated

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 deployagent endpoint, which could lead to information disclosure.

Affected Software

136 affected components
Checkmk Checkmk<2.4.0p23, <2.3.0p43
Checkmk Checkmk=2.2.0
Checkmk Checkmk=2.2.0-b1
Checkmk Checkmk=2.2.0-b2
Checkmk Checkmk=2.2.0-b3
Checkmk Checkmk=2.2.0-b4
Checkmk Checkmk=2.2.0-b5
Checkmk Checkmk=2.2.0-b6
Checkmk Checkmk=2.2.0-b7
Checkmk Checkmk=2.2.0-b8
Checkmk Checkmk=2.2.0-i1
Checkmk Checkmk=2.2.0-p1
Checkmk Checkmk=2.2.0-p10
Checkmk Checkmk=2.2.0-p11
Checkmk Checkmk=2.2.0-p12
Checkmk Checkmk=2.2.0-p13
Checkmk Checkmk=2.2.0-p14
Checkmk Checkmk=2.2.0-p15
Checkmk Checkmk=2.2.0-p16
Checkmk Checkmk=2.2.0-p17
Checkmk Checkmk=2.2.0-p18
Checkmk Checkmk=2.2.0-p19
Checkmk Checkmk=2.2.0-p2
Checkmk Checkmk=2.2.0-p20
Checkmk Checkmk=2.2.0-p21
Checkmk Checkmk=2.2.0-p22
Checkmk Checkmk=2.2.0-p23
Checkmk Checkmk=2.2.0-p24
Checkmk Checkmk=2.2.0-p25
Checkmk Checkmk=2.2.0-p26
Checkmk Checkmk=2.2.0-p27
Checkmk Checkmk=2.2.0-p28
Checkmk Checkmk=2.2.0-p29
Checkmk Checkmk=2.2.0-p3
Checkmk Checkmk=2.2.0-p30
Checkmk Checkmk=2.2.0-p31
Checkmk Checkmk=2.2.0-p32
Checkmk Checkmk=2.2.0-p33
Checkmk Checkmk=2.2.0-p34
Checkmk Checkmk=2.2.0-p35
Checkmk Checkmk=2.2.0-p36
Checkmk Checkmk=2.2.0-p37
Checkmk Checkmk=2.2.0-p38
Checkmk Checkmk=2.2.0-p39
Checkmk Checkmk=2.2.0-p4
Checkmk Checkmk=2.2.0-p40
Checkmk Checkmk=2.2.0-p41
Checkmk Checkmk=2.2.0-p42
Checkmk Checkmk=2.2.0-p43
Checkmk Checkmk=2.2.0-p44
Checkmk Checkmk=2.2.0-p45
Checkmk Checkmk=2.2.0-p46
Checkmk Checkmk=2.2.0-p47
Checkmk Checkmk=2.2.0-p5
Checkmk Checkmk=2.2.0-p6
Checkmk Checkmk=2.2.0-p7
Checkmk Checkmk=2.2.0-p8
Checkmk Checkmk=2.2.0-p9
Checkmk Checkmk=2.3.0
Checkmk Checkmk=2.3.0-b1
Checkmk Checkmk=2.3.0-b2
Checkmk Checkmk=2.3.0-b3
Checkmk Checkmk=2.3.0-b4
Checkmk Checkmk=2.3.0-b5
Checkmk Checkmk=2.3.0-b6
Checkmk Checkmk=2.3.0-p1
Checkmk Checkmk=2.3.0-p10
Checkmk Checkmk=2.3.0-p11
Checkmk Checkmk=2.3.0-p12
Checkmk Checkmk=2.3.0-p13
Checkmk Checkmk=2.3.0-p14
Checkmk Checkmk=2.3.0-p15
Checkmk Checkmk=2.3.0-p16
Checkmk Checkmk=2.3.0-p17
Checkmk Checkmk=2.3.0-p18
Checkmk Checkmk=2.3.0-p19
Checkmk Checkmk=2.3.0-p2
Checkmk Checkmk=2.3.0-p20
Checkmk Checkmk=2.3.0-p21
Checkmk Checkmk=2.3.0-p22
Checkmk Checkmk=2.3.0-p23
Checkmk Checkmk=2.3.0-p24
Checkmk Checkmk=2.3.0-p25
Checkmk Checkmk=2.3.0-p26
Checkmk Checkmk=2.3.0-p27
Checkmk Checkmk=2.3.0-p28
Checkmk Checkmk=2.3.0-p29
Checkmk Checkmk=2.3.0-p3
Checkmk Checkmk=2.3.0-p30
Checkmk Checkmk=2.3.0-p31
Checkmk Checkmk=2.3.0-p32
Checkmk Checkmk=2.3.0-p33
Checkmk Checkmk=2.3.0-p34
Checkmk Checkmk=2.3.0-p35
Checkmk Checkmk=2.3.0-p36
Checkmk Checkmk=2.3.0-p37
Checkmk Checkmk=2.3.0-p38
Checkmk Checkmk=2.3.0-p39
Checkmk Checkmk=2.3.0-p4
Checkmk Checkmk=2.3.0-p40
Checkmk Checkmk=2.3.0-p41
Checkmk Checkmk=2.3.0-p42
Checkmk Checkmk=2.3.0-p5
Checkmk Checkmk=2.3.0-p6
Checkmk Checkmk=2.3.0-p7
Checkmk Checkmk=2.3.0-p8
Checkmk Checkmk=2.3.0-p9
Checkmk Checkmk=2.4.0
Checkmk Checkmk=2.4.0-b1
Checkmk Checkmk=2.4.0-b2
Checkmk Checkmk=2.4.0-b3
Checkmk Checkmk=2.4.0-b4
Checkmk Checkmk=2.4.0-b5
Checkmk Checkmk=2.4.0-b6
Checkmk Checkmk=2.4.0-p1
Checkmk Checkmk=2.4.0-p10
Checkmk Checkmk=2.4.0-p11
Checkmk Checkmk=2.4.0-p12
Checkmk Checkmk=2.4.0-p13
Checkmk Checkmk=2.4.0-p14
Checkmk Checkmk=2.4.0-p15
Checkmk Checkmk=2.4.0-p16
Checkmk Checkmk=2.4.0-p17
Checkmk Checkmk=2.4.0-p18
Checkmk Checkmk=2.4.0-p19
Checkmk Checkmk=2.4.0-p2
Checkmk Checkmk=2.4.0-p20
Checkmk Checkmk=2.4.0-p21
Checkmk Checkmk=2.4.0-p22
Checkmk Checkmk=2.4.0-p3
Checkmk Checkmk=2.4.0-p4
Checkmk Checkmk=2.4.0-p5
Checkmk Checkmk=2.4.0-p6
Checkmk Checkmk=2.4.0-p7
Checkmk Checkmk=2.4.0-p8
Checkmk Checkmk=2.4.0-p9

Event History

Mar 13, 2026
CVE Published
via MITRE·09:40 AM
Data Sourced
via MITRE·09:40 AM
DescriptionWeakness
Data Sourced
via NVD·07:54 PM
DescriptionSeverityWeaknessAffected Software

Frequently Asked Questions

1

What is the severity of CVE-2026-2859?

CVE-2026-2859 has been classified as a medium severity vulnerability that affects specific versions of Checkmk.

2

How do I fix CVE-2026-2859?

To fix CVE-2026-2859, update your Checkmk installation to versions 2.4.0p23 or higher, or 2.3.0p43 or higher.

3

Which versions of Checkmk are affected by CVE-2026-2859?

CVE-2026-2859 affects Checkmk versions 2.4.0 before 2.4.0p23, 2.3.0 before 2.3.0p43, and 2.2.0.

4

What type of access can attackers gain from CVE-2026-2859?

Attackers exploiting CVE-2026-2859 can perform unauthenticated host enumeration, leading to the exposure of existing hosts.

5

Is there a workaround for CVE-2026-2859 until a fix is applied?

There are no known workarounds for CVE-2026-2859; upgrading to a fixed version is the recommended action.

Company

Resources

Contact

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