Flatsome <= 3.17.5 - Unauthenticated PHP Object Injection

9.8
Deserialization of Untrusted Data
CVE CVE-2023-40555
CVSS 9.8 (Critical)
Publicly Published September 5, 2023
Last Updated January 22, 2024
Researcher Rafie Muhammad - Awesome Motive, Inc.

Description

The Flatsome theme for WordPress is vulnerable to PHP Object Injection in versions up to, and including, 3.17.5 via deserialization of untrusted input. This allows unauthenticated attackers to inject a PHP Object. If a POP chain is present via an additional plugin or theme installed on the target system, it could allow the attacker to delete arbitrary files, retrieve sensitive data, or execute code.

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Vulnerability Details for Flatsome

Software Type Theme
Software Slug flatsome
Patched? Yes
Remediation Update to version 3.17.6, or a newer patched version
Affected Version
  • <= 3.17.5
Patched Version
  • 3.17.6

Recent vulnerabilities in Flatsome

# Title CVE ID CVSS Researchers Date
1 Flatsome <= 3.20.5 - Missing Authorization CVE-2026-57729 5.3 Bonds July 6, 2026
2 Flatsome <= 3.20.5 - Reflected Cross-Site Scripting CVE-2026-57728 6.1 Bonds July 6, 2026
3 Flatsome <= 3.20.5 - Missing Authorization CVE-2026-57730 4.3 Bonds July 1, 2026
4 Flatsome <= 3.20.5 - Missing Authorization CVE-2026-57731 4.3 Bonds July 1, 2026
5 Flatsome <= 3.20.5 - Authenticated (Contributor+) Stored Cross-Site Scripting CVE-2026-28083 6.4 João Pedro Soares de Alcântara October 6, 2025
6 Flatsome <= 3.20.0 - Authenticated (Contributor+) Stored Cross-Site Scripting via Shortcode CVE-2025-8684 6.4 stealthcopter September 4, 2025
7 Flatsome <= 3.19.6 - Missing Authorization CVE-2026-31915 5.3 Ananda Dhakal October 24, 2024
8 Flatsome | Multi-Purpose Responsive WooCommerce Theme <= 3.18.7 - Authenticated (Contributor+) Stored Cross-Site Scripting via Multiple Shortcodes CVE-2024-5346 6.4 wesley (wcraft) June 21, 2024
9 Flatsome <= 3.18.7 - Authenticated (Contributor+) Stored Cross-Site Scripting via Shortcode CVE-2024-5156 6.4 stealthcopter June 19, 2024
10 Flatsome <= 3.16.8 - Reflected Cross-Site Scripting in UX Builder CVE-2023-28994 6.1 Rafie Muhammad April 25, 2023

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