CVE-2026-49108: WordPress Moderno theme < 1.43 - PHP Object Injection vulnerability

Synopsis

PHP Object Injection is a class of vulnerability where unsanitized user input is passed to PHP's unserialize() function, allowing an attacker to craft a malicious serialized payload and manipulate the application's runtime objects. This vulnerability in the Moderno WordPress theme (versions below 1.43) is reachable over the network and requires no authentication whatsoever. Successful exploitation gives an attacker full control over confidentiality, integrity, and availability of the affected application, up to and including remote code execution when a suitable gadget chain is present in the environment. A patched-image rebuild at version 1.43 is available on HarborGuard for environments running an affected version of this theme.

HarborGuard Coverage

Exploit Conditions

• Network reachabilityRequired

  The vulnerable endpoint is exposed over the network, meaning an attacker can send a crafted request from any internet-accessible location without requiring physical or local access.

• AuthenticationNot required

  No account or credentials of any kind are needed to trigger the deserialization of attacker-controlled input.

• Victim interactionNot required

  The attack is fully automated and does not require any user or administrator to click a link, open a file, or take any other action.

• Attack complexityDetail

  Exploitation is reliable and condition-free: no race conditions, memory layout dependencies, or special environmental factors need to align for the attack to succeed.

Blast Radius

• Reads arbitrary files on the server, including wp-config.php, which contains database credentials and authentication keys.
• Writes or modifies files on the server if a gadget chain enabling filesystem writes is present, allowing backdoor implantation.
• Executes arbitrary operating system commands through a gadget chain, giving full remote code execution on the host running PHP.
• Crashes or degrades the WordPress application by triggering destructors that exhaust memory or corrupt application state.