CVE-2026-20915
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedStored cross-site scripting (XSS) in Checkmk version 2.5.0 (beta) before 2.5.0b2 allows authenticated users with permission to create pending changes to inject malicious JavaScript into the Pending Changes sidebar, which will execute in the browsers of other users viewing the sidebar.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceStored XSS vulnerability in Checkmk 2.5.0 beta versions before 2.5.0b2 allows authenticated users with 'create pending changes' permission to inject malicious JavaScript into the Pending Changes sidebar, which then executes in the browsers of other users viewing that sidebar.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data= 2.5.0CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- Low
- User interaction
- Required
- Scope
- Changed
- Confidentiality
- Low
- Integrity
- Low
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify installed Checkmk versionUse the Checkmk web interface (Help > About) or run 'cmk --version' at the command line to determine the exact version numberAffected if The version is 2.5.0 (any beta build before 2.5.0b2)
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Verify user permissions for pending changesNavigate to User Administration > Roles and review the permissions assigned to user roles, specifically checking for 'Create pending changes' or similar permissionAffected if Users have the 'create pending changes' permission enabled for their role
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Confirm Pending Changes sidebar is activeLog in as a user with pending changes permissions and check if the Pending Changes sidebar is visible in the web interfaceAffected if The Pending Changes sidebar is displayed to users
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Check for suspicious pending changes entriesReview the Pending Changes sidebar content for any unexpected or encoded JavaScript patterns that may indicate injected payloadsAffected if Unexpected content containing script tags, event handlers, or javascript: URIs is present in pending changes
A user is affected if they run Checkmk version 2.5.0 (beta before 2.5.0b2) and have users with the 'create pending changes' permission viewing the Pending Changes sidebar.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor dataUpgrade to Checkmk version 2.5.0b2 or later. Until then, restrict the 'create pending changes' permission to trusted users only and monitor for suspicious user activity in the Pending Changes feature.
- Consultation4.0 h
- Implementation8.0 h
- Testing4.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $5,120.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-20915 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-20915 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
- No spam, self-promotion, credentials, or personal data