CVE-2026-105651 in Ghost
Summary
by MITRE • 10/06/2026
Ghost is a Node.js content management system. From 5.94.0 until 6.64.0, when creating a bookmark card, Ghost could store non-image files fetched from an external website as bookmark icons or thumbnails. This allowed any staff user, including Contributors, to host arbitrary HTML on the site's domain, possibly resulting in compromise of other staff users' admin sessions. This issue is fixed in version 6.64.0.
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Analysis
by VulDB Data Team • 10/06/2026
The vulnerability identified within Ghost content management systems between versions 5.94.0 and 6.64.0 represents a significant security flaw rooted in improper input validation during the processing of external resources. Specifically, when an administrator or staff member creates a bookmark card by providing a URL to be fetched and displayed as a thumbnail or icon, the application fails to adequately verify the content type of the retrieved file. Instead of strictly enforcing that only image files such as JPEG, PNG, or GIF are accepted for display in this context, the system allows non-image files, including HTML documents, to be stored and served directly from the Ghost instance's domain. This behavior deviates from standard security practices which dictate that user-supplied external content must be sanitized and validated against a strict allowlist of expected file types before being persisted or rendered by the server.
The operational impact of this flaw is severe because it enables an attacker with staff-level privileges, including those with the lowest privilege level such as Contributors, to host arbitrary HTML code on the site's primary domain. By crafting a malicious URL that points to a remote resource containing script tags and other executable content, or by exploiting server-side rendering behaviors if applicable, the attacker can effectively perform Cross-Site Scripting attacks against other staff users who visit pages where these bookmark cards are rendered. Since the malicious HTML is served from the same origin as the Ghost admin interface, it bypasses Same-Origin Policy protections that would otherwise prevent scripts loaded from different domains from accessing sensitive cookies or session tokens. This allows the attacker to steal administrative sessions, hijack user accounts, and potentially escalate privileges within the application environment.
From a classification perspective, this vulnerability aligns with CWE-20 Improper Input Validation, as the system fails to restrict input based on expected data types during the fetching process. It also maps closely to CWE-79 Cross-site Scripting (XSS), specifically in scenarios where untrusted data is stored and later rendered without proper encoding or validation. In terms of offensive security frameworks, this behavior facilitates attacks consistent with MITRE ATT&CK technique T1059 Command and Scripting Interpreter if the HTML contains executable scripts that interact with the browser environment to exfiltrate data or perform actions on behalf of the victim user. The ability for lower-privileged users like Contributors to execute these actions highlights a failure in Access Control mechanisms, potentially relating to CWE-284 Improper Access Control, as the system does not sufficiently restrict what types of external resources can be ingested based on the user's role or intent.
To mitigate this vulnerability and prevent similar issues in future development cycles, it is imperative that developers implement strict content-type validation when fetching external URLs for use as thumbnails or icons. The application should verify the MIME type returned by the remote server against a whitelist of safe image formats before storing or displaying them. Additionally, implementing Content Security Policy headers can help mitigate the impact of any residual XSS vectors by restricting where scripts and other resources can be loaded from. For organizations currently running affected versions, immediate upgrading to version 6.64.0 is required as this release contains the necessary patches to enforce these validations. Until an upgrade is performed, administrators should restrict access to bookmark creation features or manually audit any existing bookmarks for suspicious external sources that could serve malicious content.