Is CVE-2026-8833 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-8833 being exploited in the wild.

How severe is CVE-2026-8833?

Informational severity, with a CVSS score of 8.5, published 8 June 2026.

Which products and versions are affected?

Checkmk GmbH Checkmk < 2.5.0p5, < 2.4.0p31, < 2.3.0p48, all 2.2.0 versions.

Is there a fix for CVE-2026-8833?

A patch was published on 2026-05-18: Vendor released fix (Werk #20002) Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-8833 attacked?

It is attacked over the network, in a network appliance.

Am I affected by CVE-2026-8833?

Check whether anything you run is named in the advisory. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-8833: Checkmk cross-site scripting via URL validation bypass

Q: Is there a fix for CVE-2026-8833?

A patch was published on 2026-05-18: Vendor released fix (Werk #20002) Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

Q: How is CVE-2026-8833 attacked?

It is attacked over the network, in a network appliance.

Q: Am I affected by CVE-2026-8833?

Check whether anything you run is named in the advisory. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-8833 · Severity: info · CVSS 8.5 · Published 2026-06-08

Checkmk, a popular IT infrastructure monitoring platform, contains a security flaw in how it validates web links. An authorized user can bypass security checks to insert malicious links into the system. If another user clicks on one of these links, an attacker could potentially take control of their session or steal sensitive information.

Quick answers

Is CVE-2026-8833 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-8833 being exploited in the wild.
How severe is CVE-2026-8833?: Informational severity, with a CVSS score of 8.5, published 8 June 2026.
Which products and versions are affected?: Checkmk GmbH Checkmk < 2.5.0p5, < 2.4.0p31, < 2.3.0p48, all 2.2.0 versions.
Is there a fix for CVE-2026-8833?: A patch was published on 2026-05-18: Vendor released fix (Werk #20002) Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-8833 attacked?: It is attacked over the network, in a network appliance.
Am I affected by CVE-2026-8833?: Check whether anything you run is named in the advisory. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

A cross-site scripting (XSS) vulnerability exists in Checkmk due to improper neutralization of HTML-encoded characters within the URL validation function. An authenticated attacker can bypass the validation mechanism by using encoded characters to inject malicious 'javascript:' URIs. When a victim interacts with the crafted link, the malicious script executes in the context of their browser session. This can lead to full session compromise or unauthorized actions performed on behalf of the victim. The issue is fixed in versions 2.5.0p5, 2.4.0p31, and 2.3.0p48.

Affected products

Checkmk GmbH Checkmk < 2.5.0p5, < 2.4.0p31, < 2.3.0p48, all 2.2.0 versions

Timeline

2026-05-18: patched: Vendor released fix (Werk #20002)
2026-06-08: disclosed: CVE published to NVD

References

https://checkmk.com/werk/20002

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