CVE-2026-16297 Overview
CVE-2026-16297 affects the Clearfy Cache WordPress plugin in versions before 2.4.3. The plugin fails to restrict allowed classes when unserializing settings-import data. Users with administrator access can exploit this weakness to perform PHP Object Injection attacks. When a suitable gadget chain exists in the environment, the flaw may escalate to remote code execution on the underlying host.
The vulnerability is classified under [CWE-502] Deserialization of Untrusted Data. It requires authenticated administrator privileges, which limits mass exploitation but remains relevant in multi-admin or compromised-credential scenarios.
Critical Impact
Authenticated administrators can trigger PHP Object Injection through settings-import data, potentially leading to remote code execution when compatible gadget chains are present.
Affected Products
- Clearfy Cache WordPress plugin versions prior to 2.4.3
- WordPress installations with the vulnerable plugin activated
- Environments containing PHP object gadget chains reachable at runtime
Discovery Timeline
- 2026-08-03 - CVE-2026-16297 published to NVD
- 2026-08-03 - Last updated in NVD database
Technical Details for CVE-2026-16297
Vulnerability Analysis
The Clearfy Cache plugin exposes a settings-import feature that accepts serialized PHP data from an administrator. The import handler passes attacker-controlled input to unserialize() without restricting the allowed classes through the allowed_classes option introduced in PHP 7.
When PHP deserializes an object, it invokes magic methods such as __wakeup(), __destruct(), and __toString() depending on how the object is subsequently used. An attacker who crafts a serialized payload can instantiate arbitrary classes loaded within the WordPress runtime, including plugin, theme, and core classes. If any reachable class chains these magic methods into sensitive sinks such as eval(), include(), file writes, or system calls, the attacker achieves remote code execution.
Exploitation requires administrator privileges, which raises the barrier but does not eliminate risk. Compromised administrator credentials, insider threats, and stacked vulnerabilities that grant administrator access all convert this issue into a viable code-execution primitive.
Root Cause
The root cause is unsafe deserialization [CWE-502]. The plugin invokes PHP's unserialize() on import data without passing ['allowed_classes' => false] or implementing an allowlist. This design accepts any class definition present in the PHP process at import time.
Attack Vector
An authenticated administrator submits a crafted serialized payload through the plugin's settings-import functionality. The plugin deserializes the payload, instantiating attacker-selected objects. Object destruction or property access then triggers magic methods that chain into a gadget available in the WordPress environment. The result depends on the gadget chain but can include arbitrary file writes, arbitrary function execution, or full remote code execution.
No verified public exploit code is available. Refer to the WPScan Vulnerability Report for advisory details.
Detection Methods for CVE-2026-16297
Indicators of Compromise
- Unexpected settings-import events in the Clearfy Cache plugin logs or WordPress admin activity records
- Serialized PHP payloads containing object markers such as O: or C: submitted to plugin import endpoints
- New or modified PHP files under wp-content/ following an administrator settings-import action
- Outbound network connections originating from the php-fpm or web server process shortly after an import event
Detection Strategies
- Inspect HTTP POST bodies to Clearfy Cache admin-ajax or import endpoints for serialized object signatures
- Alert on file creation or modification within WordPress plugin and upload directories tied to the web server process
- Correlate WordPress administrator sessions with subsequent process spawns from the PHP interpreter
Monitoring Recommendations
- Enable and centrally forward WordPress audit logs, including plugin settings changes and import operations
- Monitor web server access logs for requests to Clearfy Cache endpoints preceding versions 2.4.3
- Track administrator account activity and flag settings-import actions performed outside change windows
How to Mitigate CVE-2026-16297
Immediate Actions Required
- Update the Clearfy Cache plugin to version 2.4.3 or later on all WordPress sites
- Audit administrator accounts and remove or rotate credentials for unused or shared identities
- Review recent settings-import activity for unexpected serialized payloads
- Restrict administrator access to trusted personnel and enforce multi-factor authentication
Patch Information
Upgrade the Clearfy Cache plugin to version 2.4.3 or later. This release restricts the classes permitted during deserialization of settings-import data, eliminating the object injection primitive. See the WPScan Vulnerability Report for advisory references.
Workarounds
- Deactivate the Clearfy Cache plugin until version 2.4.3 or later can be deployed
- Block access to plugin import endpoints at the web application firewall for non-administrative source addresses
- Enforce least privilege by minimizing the number of WordPress accounts with the administrator role
# Update the Clearfy Cache plugin via WP-CLI
wp plugin update clearfy --version=2.4.3
# Verify installed version
wp plugin get clearfy --field=version
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
