Ghost CMS CVE-2026-104413

Exploitation requires an authenticated low-privileged account (PR:L) - specifically any staff user including a Contributor - on the Ghost instance, so this is not remotely exploitable by anonymous internet users. The specific trigger is the bookmark card feature's image-fetching behavior: the attacker creates a bookmark card whose icon/thumbnail references an external URL that returns a non-image file, which Ghost stores and later renders. Realized impact additionally depends on a higher-privileged staff user (admin/editor) passively viewing the stored card in the admin interface (UI:P). Limiting factors: the insider-account requirement sharply narrows the threat population to instances that provision Contributor/staff accounts for semi-trusted authors, and the required victim view means purely automated mass exploitation is not possible. Affected deployments are Ghost 5.94.0 up to (not including) 6.64.0.

This is a credible medium-to-high priority issue for organizations running Ghost multi-author instances, but not a drop-everything emergency. The CVSS 4.0 base score of 8.5 is driven by high confidentiality and integrity impact (VC:H/VI:H) over the network (AV:N) with low complexity (AC:L), but it is materially gated by PR:L (the attacker must already hold a low-privileged staff/Contributor account) and UI:P (a victim staff user must passively trigger the stored payload by viewing the affected content). No EPSS score, SSVC decision, KEV listing, or POC was provided in the input; per precision rules this is 'no public exploit identified at time of analysis.' The absence of KEV and POC signals, combined with the insider-authentication precondition, means real-world risk is concentrated in environments that grant Contributor/staff accounts to semi-trusted or external authors - a common Ghost deployment pattern. Conflicting/missing-signal note: exploitation probability (EPSS) is not supplied, so likelihood cannot be quantified; risk here rests on the authenticated-insider threat model rather than mass internet-facing exploitation. A patch is available from the vendor, which should be the primary mitigation.

A malicious or compromised Contributor-level user creates a bookmark card that points its icon/thumbnail fetch at an attacker-controlled external URL serving a non-image file containing HTML/JavaScript. When an administrator or editor later views that post or card in the Ghost admin interface, the stored script executes in their authenticated browser context, hijacking the higher-privileged admin session. No public exploit code was identified at time of analysis; exploitation is network-based but requires the victim staff user to view the malicious content (UI:P).