CVE-2026-39567: Santé PHP Object Injection Vulnerability

CVE-2026-39567 Overview

CVE-2026-39567 is an unauthenticated PHP Object Injection vulnerability affecting the Santé WordPress theme in versions 1.5.1 and earlier. The flaw stems from insecure deserialization of user-controlled input [CWE-502], allowing remote attackers to inject crafted PHP objects without authentication. Successful exploitation can lead to arbitrary code execution, data tampering, and full compromise of the underlying WordPress site. The vulnerability is network-accessible and requires no user interaction, though successful exploitation depends on the presence of a suitable property-oriented programming (POP) gadget chain within the WordPress installation or its plugins.

Critical Impact
Unauthenticated remote attackers can inject malicious PHP objects to achieve code execution and full compromise of vulnerable WordPress sites running Santé theme <= 1.5.1.

Affected Products

Santé WordPress Theme versions <= 1.5.1
WordPress installations using the Santé theme
Sites with bundled or third-party plugins providing exploitable PHP gadget chains

Discovery Timeline

2026-06-17 - CVE-2026-39567 published to the National Vulnerability Database (NVD)
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2026-39567

Vulnerability Analysis

The Santé theme deserializes attacker-controlled input via PHP's unserialize() function without validating the data source or type. When an attacker submits a crafted serialized payload, PHP reconstructs arbitrary objects in memory. During reconstruction, magic methods such as __wakeup(), __destruct(), or __toString() execute automatically on the resulting objects. Attackers chain these magic methods through existing classes (a POP chain) to perform unintended actions, including file writes, command execution, or arbitrary SQL queries. Because the entry point requires no authentication, exploitation is reachable directly over the network.

Root Cause

The root cause is insecure deserialization of untrusted input [CWE-502]. The theme accepts serialized PHP data from an unauthenticated request channel and passes it to unserialize() without sanitization, signature verification, or schema enforcement. PHP deserialization is unsafe by design when applied to attacker-controlled data because object instantiation triggers class-defined lifecycle hooks.

Attack Vector

A remote attacker sends a crafted HTTP request containing a serialized PHP object payload to a vulnerable endpoint exposed by the Santé theme. The deserialization routine instantiates the supplied class hierarchy, triggering magic methods that operate on attacker-controlled properties. By leveraging a gadget chain from WordPress core, the theme, or any installed plugin, the attacker can pivot from object injection to file write primitives or arbitrary command execution. The attack complexity is elevated by the dependency on an available gadget chain in the target environment.

No verified proof-of-concept code is publicly available at the time of publication. For technical details, refer to the Patchstack WordPress Vulnerability advisory.

Detection Methods for CVE-2026-39567

Indicators of Compromise

HTTP requests containing serialized PHP markers such as O:, a:, or s: in query parameters, POST bodies, or cookies targeting Santé theme endpoints
Unexpected PHP files written to wp-content/uploads/ or theme directories following inbound requests
New or modified WordPress administrator accounts not created by legitimate workflows
Outbound connections from the web server process to unfamiliar hosts shortly after suspicious POST requests

Detection Strategies

Inspect web server and WAF logs for serialized PHP object patterns matching the regex O:\d+:"[A-Za-z_\\]+":\d+: in request payloads
Monitor calls to unserialize() via PHP runtime auditing or extensions such as Snuffleupagus
Correlate HTTP requests to Santé theme paths with subsequent file creation events in webroot directories

Monitoring Recommendations

Enable verbose access logging on WordPress sites using the Santé theme and forward logs to a centralized analytics platform
Alert on PHP process spawning shell interpreters such as sh, bash, or cmd.exe
Track file integrity changes within the WordPress installation directory, particularly under wp-content/themes/sante/

How to Mitigate CVE-2026-39567

Immediate Actions Required

Identify all WordPress sites running the Santé theme and confirm the installed version
Upgrade the Santé theme to a version above 1.5.1 once the vendor publishes a fix
Restrict access to vulnerable WordPress instances behind authentication or a Web Application Firewall (WAF) until patched
Review web server logs for prior exploitation attempts containing serialized PHP payloads

Patch Information

Review the Patchstack WordPress Vulnerability advisory for the current patch status and remediation guidance. Apply the vendor-supplied update as soon as it becomes available through the WordPress theme update channel.

Workarounds

Deploy WAF rules that block requests containing serialized PHP object signatures targeting WordPress theme endpoints
Disable or remove the Santé theme on non-production sites until a patched version is installed
Harden the PHP runtime by disabling unnecessary classes via disable_classes and limiting filesystem write permissions on the web server account

bash

# Example WAF rule (ModSecurity) to block serialized PHP object payloads
SecRule ARGS|REQUEST_BODY|REQUEST_COOKIES "@rx O:[0-9]+:\"[A-Za-z_\\\\]+\":[0-9]+:" \
  "id:1039567,phase:2,deny,status:403,log,\
  msg:'CVE-2026-39567: PHP object injection attempt against Sante theme'"