CVE-2026-53949 Overview
CVE-2026-53949 is an information disclosure vulnerability in Ghost, a Node.js content management system. The flaw affects versions from 5.46.1 until 6.21.2. Validation applied to filters on the public API endpoints can be partially bypassed. Attackers can reveal private fields through a brute force attack against the public API. When SQLite serves as the backing database, password hashes are fully accessible to unauthenticated network attackers. MySQL deployments lose case sensitivity on the leaked hash characters, which renders subsequent offline brute force attempts against the recovered hashes ineffective. The issue is tracked under [CWE-200: Exposure of Sensitive Information to an Unauthorized Actor].
Critical Impact
Unauthenticated remote attackers can extract user password hashes from Ghost instances backed by SQLite via filter bypass on public API endpoints.
Affected Products
- Ghost CMS versions 5.46.1 through 6.21.1
- Ghost deployments using SQLite as the database backend (full hash disclosure)
- Ghost deployments using MySQL as the database backend (partial hash disclosure)
Discovery Timeline
- 2026-06-24 - CVE-2026-53949 published to NVD
- 2026-06-24 - Last updated in NVD database
Technical Details for CVE-2026-53949
Vulnerability Analysis
Ghost exposes a public Content API that supports filter expressions to query published content. The filter parser enforces an allowlist that restricts which fields can appear in filter clauses, preventing direct queries against sensitive columns such as password. The validation implemented from version 5.46.1 onward can be partially circumvented. Attackers can construct filter expressions that reference private fields despite the restriction.
By crafting filters that compare a private field against attacker-controlled values, an attacker observes whether matching records exist based on API response differences. This oracle behavior enables a character-by-character brute force of private values, including stored password hashes. Although Ghost stores bcrypt hashes rather than plaintext credentials, recovering the full hash enables offline cracking attempts against weak passwords. The vulnerability requires no authentication and no user interaction because the public API is reachable by any network client.
Root Cause
The root cause is incomplete input validation in the filter parsing layer that handles public API requests. The allowlist intended to block references to private columns can be bypassed through specific filter constructions, allowing the underlying query builder to emit conditions against fields that should never be exposed externally.
Attack Vector
The attack is conducted entirely over the network against the unauthenticated public Content API. An attacker sends crafted filter parameters to public endpoints and analyzes response variations to infer characters of the targeted private field. The brute force completes faster against SQLite because the database preserves character case, while MySQL collations strip case information from the inferred output. See the Ghost Security Advisory GHSA-jx35-x7fj-vgpr for technical details.
Detection Methods for CVE-2026-53949
Indicators of Compromise
- High volumes of requests to Ghost public Content API endpoints containing complex or repetitive filter query parameters from a single source.
- Sequential API requests where the filter parameter differs only by a single character or value, indicating a brute force oracle attack.
- API requests referencing field names that do not appear in Ghost's documented public schema, particularly tokens resembling password or other user-table columns.
Detection Strategies
- Inspect web server and reverse proxy logs for requests to /ghost/api/content/ paths containing unusually long or encoded filter expressions.
- Correlate request rate, response size variance, and unique filter permutations from the same client to identify oracle-style enumeration.
- Compare deployed Ghost version against 6.21.2 and flag any instance running 5.46.1 through 6.21.1 as exposed.
Monitoring Recommendations
- Enable verbose access logging on the Ghost application and any fronting CDN or load balancer to retain full query string contents.
- Alert on sustained request bursts targeting Content API endpoints from non-cached, non-browser user agents.
- Audit Ghost user records for unexpected password resets, session creations, or administrative privilege changes that may follow hash recovery.
How to Mitigate CVE-2026-53949
Immediate Actions Required
- Upgrade Ghost to version 6.21.2 or later, which contains the fix for the filter validation bypass.
- Rotate all user passwords and invalidate active sessions on any SQLite-backed Ghost instance that was internet-exposed prior to patching.
- Restrict public API exposure at the network edge until the upgrade is applied, blocking unauthenticated filter parameters where feasible.
Patch Information
The vulnerability is fixed in Ghost version 6.21.2. The patch tightens validation on filter expressions submitted to the public API to prevent references to private fields. Refer to the Ghost Security Advisory GHSA-jx35-x7fj-vgpr for the official remediation guidance.
Workarounds
- Place a web application firewall in front of Ghost and block requests where the filter query parameter contains references to non-public field names such as password.
- Rate limit unauthenticated requests to Content API endpoints to slow brute force enumeration against the filter oracle.
- Migrate development and small-production deployments off SQLite to reduce full-hash disclosure risk until the upgrade can be applied.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
