CVE-2026-39550: Aperitif Object Injection Vulnerability

CVE-2026-39550 Overview

CVE-2026-39550 is a PHP Object Injection vulnerability in the Elated-Themes Aperitif WordPress theme. The flaw stems from insecure deserialization of untrusted data [CWE-502] and affects all versions of Aperitif up to and including 1.6. An unauthenticated attacker can submit crafted serialized payloads to a vulnerable entry point, triggering object instantiation inside the PHP runtime. When combined with a suitable gadget chain present in WordPress core, other plugins, or installed themes, this can lead to arbitrary code execution, file manipulation, or full site compromise.

Critical Impact
Unauthenticated attackers can inject malicious PHP objects over the network, potentially achieving remote code execution and full compromise of affected WordPress sites running Aperitif 1.6 or earlier.

Affected Products

Elated-Themes Aperitif WordPress theme
All versions from unspecified initial release through 1.6
WordPress sites with the vulnerable theme installed and active

Discovery Timeline

2026-06-02 - CVE-2026-39550 published to the National Vulnerability Database
2026-06-02 - Last updated in NVD database

Technical Details for CVE-2026-39550

Vulnerability Analysis

The Aperitif theme processes attacker-controllable input through PHP's unserialize() function without validating the source or structure of the serialized data. PHP deserialization reconstructs object instances and invokes magic methods such as __wakeup(), __destruct(), and __toString() during this process. When an attacker controls the serialized stream, they control which classes are instantiated and which property values those objects carry.

This primitive becomes exploitable when a usable gadget chain exists in the loaded PHP environment. WordPress installations typically load dozens of classes from core, plugins, and other themes, expanding the gadget surface significantly. Successful exploitation can lead to arbitrary file writes, SQL query manipulation, or remote code execution depending on the available chain.

Root Cause

The root cause is improper handling of serialized input. Aperitif accepts attacker-supplied data and passes it to a deserialization routine without enforcing an allowlist of expected classes, validating integrity, or using safer formats such as JSON. This pattern is the canonical instance of [CWE-502] Deserialization of Untrusted Data.

Attack Vector

The vulnerability is reachable over the network without authentication or user interaction. An attacker crafts a serialized PHP payload containing one or more class instances that trigger a destructive gadget chain during deserialization. The payload is delivered through an HTTP request to the vulnerable endpoint exposed by the theme. High attack complexity reflects the need to identify a working gadget chain within the target's specific plugin and theme combination. Refer to the Patchstack Vulnerability Report for additional technical context.

Detection Methods for CVE-2026-39550

Indicators of Compromise

HTTP requests containing serialized PHP patterns such as O:, a:, or s: followed by class names and length prefixes in query strings, POST bodies, or cookies
Unexpected PHP files written under wp-content/uploads/, wp-content/themes/aperitif/, or other writable directories
New or modified administrator accounts in wp_users without a corresponding audit trail
Outbound connections from the web server to attacker-controlled infrastructure following suspicious POST requests

Detection Strategies

Inspect web server and WordPress access logs for serialized payload signatures targeting Aperitif endpoints
Monitor PHP error logs for unserialize() warnings, class-not-found errors, or unexpected __wakeup() or __destruct() failures
Deploy file integrity monitoring against the theme directory and the broader wp-content/ tree
Correlate web request anomalies with subsequent process execution from php-fpm or the web server user

Monitoring Recommendations

Enable WordPress audit logging to capture configuration changes, user creation, and plugin or theme modifications
Forward web server, PHP, and WordPress logs to a centralized analytics platform for retention and correlation
Alert on outbound network connections originating from web application processes to non-allowlisted destinations
Track requests to theme-specific AJAX actions and admin-ajax handlers for abnormal volume or payload size

How to Mitigate CVE-2026-39550

Immediate Actions Required

Identify all WordPress instances running the Aperitif theme and confirm the installed version
Deactivate and remove the Aperitif theme on sites where an updated version is not yet available
Restrict access to WordPress administrative and AJAX endpoints using IP allowlists or a web application firewall
Review the site for indicators of prior exploitation, including unauthorized administrative accounts and unexpected PHP files

Patch Information

At the time of publication, no fixed version is referenced in the available advisory data. Site operators should monitor the Patchstack Vulnerability Report and the vendor's distribution channel for an updated release that supersedes version 1.6.

Workarounds

Deploy WAF rules that block requests containing serialized PHP object signatures such as O:\d+:" targeting the Aperitif theme
Disable or remove the theme until a patched version is released and validated
Apply virtual patching through a managed WordPress security service such as Patchstack
Enforce least privilege on the PHP process and database user to limit post-exploitation impact

bash

# Example ModSecurity rule blocking PHP object injection patterns
SecRule ARGS|REQUEST_COOKIES|REQUEST_HEADERS "@rx O:\d+:\"[A-Za-z_\\\\]+\":\d+:" \
    "id:1039550,phase:2,deny,status:403,log,\
    msg:'CVE-2026-39550 PHP object injection attempt against Aperitif theme'"