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Cross-site Scripting (XSS)Weakness · CWE-79

CVE-2026-45368

HIGH · 8.4 CVSS v4.0 Published 2026-07-16
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
88/100
Remediation priority · High
Remotely reachable 5 weeks old

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 · unedited
Kirby is an open-source content management system. In versions prior to 4.9.1 and 5.4.1, the underlying URL methods for the KirbyTags and image blocks components did not filter out malicious URL values that resolve to script execution. The vulnerability affects four first-party Kirby renderers that produce `<a href="…">` output from editor-supplied field values: the (`link: …)` KirbyTag, the `link`: parameter of the `(image: …)` KirbyTag when it does not resolve to a known file or `self`, the `link` field of the built-in image block, and the HTML importer for the `blocks` field (which accepted the same malicious input as the image block `link` field). While simple `avascript:` URLs were already deactivated by treating them as a relative path and prepending a single slash to the URL, the use of URLs of the format `javascript://x%0A…` bypasses this protection. The `vbscript:`, `data:`, `livescript:`, `mocha:` and `jar:` schemes are affected by the same underlying gap. This issue has been fixed in versions 4.9.1 and 5.4.1.

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 confidence

Cross-Site Scripting (XSS) vulnerability in Kirby CMS where URL filtering for KirbyTags (link: and image:) and image blocks can be bypassed using encoded newlines (%0A) in dangerous URL schemes like javascript:, vbscript:, data:, livescript:, mocha:, and jar:. Simple javascript: URLs were blocked by prepending a slash, but javascript://x%0A… bypasses this protection.

MitigationUpgrade Kirby to version 4.9.1 or 5.4.1 (depending on major version line) to receive the patched URL filtering. Review any custom KirbyTags or plugins that handle URLs for similar issues.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS 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
Authentication
X
User interaction
A
Scope
X

CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:A/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

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 checks

Work through these to decide whether this CVE applies to you.

  1. Identify Kirby CMS version
    Check the composer.json file in the Kirby root directory, or look for the Kirby version in the /kirby/composer.json file. Look for the 'kirby/framework' or 'getkirby/cms' package version.
    Affected if Running Kirby versions prior to 4.9.1 (v4) or 5.4.1 (v5)
  2. Check for link: KirbyTag usage
    Search project files for occurrences of 'link:' KirbyTag syntax in content files, templates, or blueprints. Look for patterns like '(link: ...)' in .md files or in PHP template code.
    Affected if The link: KirbyTag is used to render hyperlinks in content
  3. Check for image: KirbyTag with link parameter
    Search for image: KirbyTag usage with link parameter, such as '(image: filename.jpg link: ...)' in content files or templates.
    Affected if Image KirbyTags include a link parameter pointing to user-supplied URLs
  4. Check for image block with link field
    Examine blueprint definitions and content files for image blocks that include a link field. Look in /site/blueprints/ for block definitions and in content .md files for block structures.
    Affected if Image blocks with configurable link fields are defined and used
  5. Check for HTML importer usage
    Search for usage of the HTML importer feature for blocks fields. Look in PHP code or configuration for 'html' importer or blocks field import functionality.
    Affected if The blocks field HTML importer is enabled and processes external HTML input

A user is affected if running a Kirby version below 4.9.1 or 5.4.1 AND any of the four affected components (link: KirbyTag, image: KirbyTag with link, image block link field, or HTML importer) handle user-supplied URLs.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade Kirby to version 4.9.1 or 5.4.1 (depending on major version line) to receive the patched URL filtering. Review any custom KirbyTags or plugins that handle URLs for similar issues.

Recommended fix High confidence

4.9.1 for Kirby 4.x branch; 5.4.1 for Kirby 5.x branch

  1. Identify the current Kirby version in use by checking the composer.json file or Kirby's version method
  2. If running Kirby 4.x: Upgrade to version 4.9.1 or later
  3. If running Kirby 5.x: Upgrade to version 5.4.1 or later
  4. Run composer update to apply the changes
  5. Verify the upgrade was successful by confirming the new Kirby version
  6. Test that the application functions correctly with the new version, particularly any areas using link: KirbyTags or image blocks with link fields

Generated from the published advisory — verify against the referenced sources before acting.

Have this fixed Scoped from the published advisory
  • Consultation3.0 h
  • Implementation4.0 h
  • Testing4.0 h
  • Review / QA2.0 h
13.0 hours of engineering $2,280
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-45368 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • 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