FedoraOperating system · Fedoraproject
CVE-2023-28439
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 · uneditedCKEditor4 is an open source what-you-see-is-what-you-get HTML editor. A cross-site scripting vulnerability has been discovered affecting Iframe Dialog and Media Embed packages. The vulnerability may trigger a JavaScript code after fulfilling special conditions: using one of the affected packages on a web page with missing proper Content Security Policy configuration; initializing the editor on an element and using an element other than `<textarea>` as a base; and destroying the editor instance. This vulnerability might affect a small percentage of integrators that depend on dynamic editor initialization/destroy mechanism. A fix is available in CKEditor4 version 4.21.0. In some rare cases, a security fix may be considered a breaking change. Starting from version 4.21.0, the Iframe Dialog plugin applies the `sandbox` attribute by default, which restricts JavaScript code execution in the iframe element. To change this behavior, configure the `config.iframe_attributes` option. Also starting from version 4.21.0, the Media Embed plugin regenerates the entire content of the embed widget by default. To change this behavior, configure the `config.embed_keepOriginalContent` option. Those who choose to enable either of the more permissive options or who cannot upgrade to a patched version should properly configure Content Security Policy to avoid any potential security issues that may arise from embedding iframe elements on their web page.
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 confidenceCKEditor4 contains a cross-site scripting vulnerability in its Iframe Dialog and Media Embed packages. The XSS triggers only when: Content Security Policy is missing or inadequate, the editor is initialized on a non-textarea element (such as a div), and the editor instance is subsequently destroyed. This allows JavaScript code execution in the affected context.
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
FedoraOperating system
= 37= 38= 39>= 4.0, < 4.21.0CVSS 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
- None
- User interaction
- Required
- Scope
- Changed
- Confidentiality
- Low
- Integrity
- Low
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/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 CKEditor versionLocate the ckeditor.js or ckeditor4.js file and check its version identifier, typically found in the file header comments or a version.js file. Alternatively, execute CKEDITOR.version in browser console if the editor is loaded.Affected if version is less than 4.21.0 (e.g., 4.20.0, 4.19.0, etc.)
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Verify editor initialization element typeSearch the application code for CKEDITOR.replace() or CKEDITOR.appendTo() calls. Examine the first parameter passed to these methods to determine the target element.Affected if the target element is a div, span, or any non-textarea element (e.g., CKEDITOR.replace('myDiv') or CKEDITOR.appendTo('myDiv', ...))
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Inspect Content Security Policy headersReview the HTTP response headers from the server serving the CKEditor page. Look for the Content-Security-Policy header and examine its directives, particularly frame-src, sandbox, and script-src.Affected if the Content-Security-Policy header is absent, or frame-src and script-src directives allow unsafe-inline or unspecified sources
You are affected if CKEditor version is below 4.21.0 AND the editor is initialized on a non-textarea element (such as a div) AND Content Security Policy is missing or inadequate.
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.
dbcve · scoped4.21.0
Upgrade CKEditor4 to version 4.21.0 or later. If upgrading is not feasible, implement proper Content Security Policy headers to restrict iframe and script execution.
CKEditor4 version 4.21.0 or later
- Upgrade CKEditor4 to version 4.21.0 or later to resolve the XSS vulnerability
- After upgrading, test the Iframe Dialog and Media Embed functionality to ensure the changes do not break existing workflows
- If the default `sandbox` attribute behavior causes issues with the Iframe Dialog plugin, configure `config.iframe_attributes` to restore the desired attributes
- If the Media Embed plugin regeneration causes issues, configure `config.embed_keepOriginalContent` to preserve original content
- Verify that Content Security Policy is properly configured on the web page as an additional defense layer
- For Fedora systems, ensure the corresponding CKEditor package updates are applied (Fedora 37, 38, 39 have the update)
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Fedora
Scoped from the published advisory
- Consultation3.0 h
- Implementation4.0 h
- Testing3.0 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 $3,408.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2023-28439 — 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-2023-28439 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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- Version or environment caveats, and links to real fixes
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