CVE-2026-40735: Reina PHP Object Injection Vulnerability

CVE-2026-40735 Overview

CVE-2026-40735 is an unauthenticated PHP Object Injection vulnerability affecting the Reina WordPress theme in versions 2.1 and earlier. The flaw stems from insecure deserialization of attacker-controlled input [CWE-502]. Remote attackers can submit crafted serialized payloads without authentication, allowing object instantiation inside the WordPress runtime. When suitable PHP gadget chains exist in the host environment, exploitation can lead to remote code execution, data tampering, or denial of service. The vulnerability carries a CVSS 3.1 base score of 8.1, reflecting network-reachable impact across confidentiality, integrity, and availability. The current EPSS probability is 0.395%, placing the issue in the 31st percentile for near-term exploitation likelihood.

Critical Impact
Unauthenticated attackers can trigger PHP object injection on WordPress sites running the Reina theme, potentially leading to arbitrary code execution depending on installed plugins and gadget chains.

Affected Products

Reina WordPress theme version 2.1
Reina WordPress theme versions prior to 2.1
WordPress installations using the vulnerable Reina theme

Discovery Timeline

2026-06-17 - CVE-2026-40735 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2026-40735

Vulnerability Analysis

The Reina theme passes untrusted input to a PHP deserialization routine without validation. PHP's unserialize() reconstructs arbitrary objects from a serialized string and invokes magic methods such as __wakeup(), __destruct(), and __toString() during object lifecycle events. Attackers exploit this behavior by crafting payloads referencing classes present in WordPress core, plugins, or the theme itself. When chained through existing classes, the deserialization process can yield file writes, SQL execution, or arbitrary command execution. The vulnerability requires no authentication, since the affected entry point accepts requests from anonymous users. Attack complexity is rated High because exploitation depends on the presence of an effective gadget chain in the target's PHP class graph.

Root Cause

The root cause is improper deserialization of user-supplied data, mapped to [CWE-502]. The theme treats serialized input as trusted and reconstructs PHP objects without type allow-listing, signature verification, or migration to a safe format such as JSON.

Attack Vector

The attack vector is network-based. An attacker sends a crafted HTTP request containing a serialized PHP object to a vulnerable endpoint exposed by the Reina theme. The server deserializes the payload, instantiates attacker-chosen classes, and triggers gadget chains during PHP object destruction. The specific request method, parameter name, and entry point are described in the Patchstack WordPress Vulnerability Report.

No verified public proof-of-concept code is available. The vulnerability mechanism centers on PHP's unserialize() function processing attacker-controlled bytes that include object type identifiers and property values. Defenders should review the Patchstack advisory for the precise affected parameter rather than rely on synthetic payload examples.

Detection Methods for CVE-2026-40735

Indicators of Compromise

HTTP requests to Reina theme endpoints containing serialized PHP markers such as O:, a:, s:, or C: in query strings, cookies, or POST bodies
Unexpected PHP errors referencing __wakeup, __destruct, or unserialize() in web server logs
New or modified PHP files under wp-content/themes/reina/ or wp-content/uploads/
Outbound connections from the web server process to unfamiliar hosts following Reina theme requests

Detection Strategies

Inspect web access logs for request parameters containing PHP serialization syntax patterns
Deploy WAF rules that block serialized PHP objects in untrusted parameters consumed by the Reina theme
Monitor for anomalous child processes spawned by the PHP-FPM or web server worker processes
Compare theme file hashes against the vendor distribution to detect tampering

Monitoring Recommendations

Enable WordPress audit logging for theme and plugin file modifications and administrative actions
Forward web server, PHP error, and WAF logs to a centralized analytics platform for correlation
Alert on first-seen User-Agent strings issuing POST requests to Reina theme endpoints
Track creation of PHP files in writable WordPress directories outside scheduled update windows

How to Mitigate CVE-2026-40735

Immediate Actions Required

Update the Reina theme to a fixed version once published by the vendor, per the Patchstack advisory
If no patched version is available, deactivate and remove the Reina theme from affected WordPress sites
Audit wp-content/ for unauthorized PHP files, web shells, or modified core files
Rotate WordPress administrator credentials, API keys, and database passwords on any potentially compromised site

Patch Information

Refer to the Patchstack WordPress Vulnerability Report for the current patch status and fixed version information. Apply the vendor-supplied update through the WordPress admin dashboard or by replacing the theme directory with the patched release.

Workarounds

Restrict access to Reina theme endpoints using a web application firewall or reverse proxy ACLs
Block requests containing serialized PHP object signatures using ModSecurity or equivalent WAF rules
Disable the Reina theme and switch to a maintained alternative until a fix is released
Apply WordPress hardening measures such as disabling file editing via define('DISALLOW_FILE_EDIT', true); in wp-config.php

bash

# Example ModSecurity rule to block serialized PHP objects in request bodies
SecRule REQUEST_BODY|ARGS|REQUEST_COOKIES "@rx O:[0-9]+:\"[a-zA-Z_\\\\]+\":[0-9]+:\{" \
  "id:1040735,phase:2,deny,status:403,log,\
   msg:'CVE-2026-40735 PHP object injection attempt against Reina theme'"