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CVE-2026-53945: CVE-2026-53945: Time-of-Check to Time-of-Use (TOCTOU) DNS Rebinding Server-Side Request Forgery in Ghost CMS

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CVE-2026-53945: Time-of-Check to Time-of-Use (TOCTOU) DNS Rebinding Server-Side Request Forgery in Ghost CMS

Vulnerability ID: CVE-2026-53945
CVSS Score: 4.0
Published: 2026-08-04

Ghost CMS is vulnerable to Server-Side Request Forgery (SSRF) in versions 6.0.9 through 6.21.1. Due to a Time-of-Check to Time-of-Use (TOCTOU) race condition in its outbound fetch validation logic, an attacker can bypass IP blocklists via DNS Rebinding. This allows unauthorized interaction with private networks and local services.

TL;DR

A DNS Rebinding vulnerability in Ghost CMS allows attackers to bypass private IP blocklists and execute SSRF requests against local networks due to a TOCTOU race condition between request validation and socket establishment.

Technical Details

  • CWE ID: CWE-367 (TOCTOU), CWE-918 (SSRF)
  • Attack Vector: Network (Unauthenticated SSRF)
  • CVSS Score: 4.0 (Medium)
  • EPSS Score: 0.00140 (0.14%)
  • Exploit Status: Proof of Concept / Technical Analysis available
  • CISA KEV Status: Not Listed

Affected Systems

  • Ghost CMS self-hosted deployments running versions 6.0.9 through 6.21.0
  • Ghost: >= 6.0.9, < 6.21.1 (Fixed in: 6.21.1)

Code Analysis

Commit: 07d6041

Fix external fetch DNS validation logic by injecting options.lookup into native HTTP configurations.

Mitigation Strategies

  • Upgrade Ghost CMS to version 6.21.1 or higher.
  • Implement network egress filters using iptables or cloud security groups to restrict outbound connections to private subnets.
  • Ensure production deployments have NODE_ENV set to production.

Remediation Steps:

  1. Navigate to the Ghost installation directory on your host server.
  2. Execute 'ghost update' to pull and install the latest security releases.
  3. Verify the running configuration environment by inspecting the startup logs for active development mode warnings.
  4. Configure cloud security rules to block outgoing traffic from the Ghost server targeting the metadata address 169.254.169.254.

References

Read the full report for CVE-2026-53945 on our website for more details including interactive diagrams and full exploit analysis.

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