CVE-2026-9549

Fix XSS in service discovery active check output

MEDIUM

4.8

CVSS Score

Published: June 8, 2026 at 12:07 PM UTC

Updated: October 23, 2026 at 10:10 PM UTC

1 product affected across 1 vendorCheckmk

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Severity

MEDIUM4.8

Exploit prediction

EPSS 0.1%

SSVC

No known exploit

Description

Stored cross-site scripting in the service discovery active check output in Checkmk <2.5.0p5, <2.4.0p31, <2.3.0p48, and all 2.2.0 versions allows an administrator who can configure active or custom checks to inject malicious HTML or JavaScript into check output that executes in the browser of an admin or a user with host read permissions when they run the check on the service discovery page.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Checkmk · Checkmk

95%

2.2.0 2.2.0 b1 2.2.0 b2 2.2.0 b3 2.2.0 b4 2.2.0 b5 2.2.0 b6 2.2.0 b7 2.2.0 b8 2.2.0 i1 2.2.0 p1 2.2.0 p10 2.2.0 p11 2.2.0 p12 2.2.0 p13 2.2.0 p14 2.2.0 p15 2.2.0 p16 2.2.0 p17 2.2.0 p18 2.2.0 p19 2.2.0 p2 2.2.0 p20 2.2.0 p21 2.2.0 p22 2.2.0 p23 2.2.0 p24 2.2.0 p25 2.2.0 p26 2.2.0 p27 2.2.0 p28 2.2.0 p29 2.2.0 p3 2.2.0 p30 2.2.0 p31 2.2.0 p32 2.2.0 p33 2.2.0 p34 2.2.0 p35 2.2.0 p36 2.2.0 p37 2.2.0 p38 2.2.0 p39 2.2.0 p4 2.2.0 p40 2.2.0 p41 2.2.0 p42 2.2.0 p43 2.2.0 p44 2.2.0 p45 2.2.0 p46 2.2.0 p47 2.2.0 p5 2.2.0 p6 2.2.0 p7 2.2.0 p8 2.2.0 p9 2.3.0 2.3.0 b1 2.3.0 b2 2.3.0 b3 2.3.0 b4 2.3.0 b5 2.3.0 b6 2.3.0 p1 2.3.0 p10 2.3.0 p11 2.3.0 p12 2.3.0 p13 2.3.0 p14 2.3.0 p15 2.3.0 p16 2.3.0 p17 2.3.0 p18 2.3.0 p19 2.3.0 p2 2.3.0 p20 2.3.0 p21 2.3.0 p22 2.3.0 p23 2.3.0 p24 2.3.0 p25 2.3.0 p26 2.3.0 p27 2.3.0 p28 2.3.0 p29 2.3.0 p3 2.3.0 p30 2.3.0 p31 2.3.0 p32 2.3.0 p33 2.3.0 p34 2.3.0 p35 2.3.0 p36 2.3.0 p37 2.3.0 p38 2.3.0 p39 2.3.0 p4 2.3.0 p40 2.3.0 p41 2.3.0 p42 2.3.0 p43 2.3.0 p44 2.3.0 p45 2.3.0 p46 2.3.0 p47 2.3.0 p5 2.3.0 p6 2.3.0 p7 2.3.0 p8 2.3.0 p9 2.4.0 2.4.0 b1 2.4.0 b2 2.4.0 b3 2.4.0 b4 2.4.0 b5 2.4.0 b6 2.4.0 p1 2.4.0 p10 2.4.0 p11 2.4.0 p12 2.4.0 p13 2.4.0 p14 2.4.0 p15 2.4.0 p16 2.4.0 p17 2.4.0 p18 2.4.0 p19 2.4.0 p2 2.4.0 p20 2.4.0 p21 2.4.0 p22 2.4.0 p23 2.4.0 p24 2.4.0 p25 2.4.0 p26 2.4.0 p27 2.4.0 p28 2.4.0 p29 2.4.0 p3 2.4.0 p30 2.4.0 p4 2.4.0 p5 2.4.0 p6 2.4.0 p7 2.4.0 p8 2.4.0 p9 2.5.0 2.5.0 b1 2.5.0 b2 2.5.0 b3 2.5.0 p1 2.5.0 p2 2.5.0 p3 2.5.0 p4

Affected range stops below 2.3.0p48, so it looks safe — our inference, not a vendor statement

Affected range stops below 2.4.0p31, so it looks safe — our inference, not a vendor statement

Affected range stops below 2.5.0p5, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

Patch and advisory references

https://checkmk.com/werk/17993

References (1)

Vendor Advisory

Source: cverecord

https://checkmk.com/werk/17993

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

4.8MEDIUMCheckmk

Vector?

Quick Info

StatusANALYZED

CWE

CWE-79

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