CVE-2026-27410 Overview
CVE-2026-27410 is an unauthenticated deserialization of untrusted data vulnerability in the Slimstat Analytics WordPress plugin in versions prior to 5.4.0. The flaw allows network-based attackers to submit crafted serialized payloads that the plugin deserializes without validation. Successful exploitation can lead to PHP object injection, enabling attackers to abuse gadget chains present in WordPress core or other installed plugins. The vulnerability is tracked under CWE-502: Deserialization of Untrusted Data.
Critical Impact
Unauthenticated attackers can trigger PHP object injection on vulnerable WordPress sites running Slimstat Analytics prior to 5.4.0, potentially leading to code execution or data tampering depending on available gadget chains.
Affected Products
- WordPress Slimstat Analytics plugin (wp-slimstat) versions prior to 5.4.0
- WordPress installations with the vulnerable plugin enabled
- Sites exposing plugin endpoints to unauthenticated network traffic
Discovery Timeline
- 2026-06-17 - CVE-2026-27410 published to NVD
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2026-27410
Vulnerability Analysis
The vulnerability stems from the plugin passing attacker-controlled input to PHP's unserialize() function or an equivalent deserialization routine. Because the input is not validated or restricted to safe classes, attackers can supply crafted serialized objects that instantiate arbitrary classes during deserialization. When these objects are destroyed or their magic methods are invoked, the resulting gadget chain can execute attacker-controlled logic. The issue is reachable without authentication, increasing exposure on any internet-facing WordPress site running the plugin.
Root Cause
The root cause is unsafe deserialization of user-supplied data within the wp-slimstat plugin. PHP's serialization format allows arbitrary object reconstruction, and the plugin does not constrain allowed classes or validate the input before processing. This pattern, classified under CWE-502, is well-documented in WordPress plugin ecosystems where serialized data flows through cookies, query parameters, or tracking payloads.
Attack Vector
The attack vector is network-based and requires no authentication or user interaction. An attacker sends a crafted HTTP request containing a serialized PHP payload to a plugin endpoint that performs deserialization. The complexity is high because successful code execution depends on the presence of a usable gadget chain in WordPress core, themes, or other installed plugins. Refer to the Patchstack advisory for technical details on the affected entry point.
No verified public exploit code is available for this CVE at the time of publication. EPSS data indicates a probability of 0.252% with a percentile of 16.26 as of 2026-06-18.
Detection Methods for CVE-2026-27410
Indicators of Compromise
- HTTP requests to wp-slimstat plugin endpoints containing serialized PHP markers such as O:, a:, or s: in parameters, cookies, or POST bodies
- Unexpected PHP errors in web server logs referencing unserialize() or __wakeup and __destruct magic methods
- Outbound network connections originating from the php-fpm or web server process to attacker-controlled hosts
- Creation or modification of PHP files under wp-content/uploads/ or plugin directories
Detection Strategies
- Inspect web access logs for unauthenticated POST or GET requests to wp-slimstat with base64-like or serialized PHP payloads
- Monitor WordPress file integrity, particularly within plugin and uploads directories, for unexpected changes
- Correlate web request anomalies with new process executions on the host running the WordPress site
Monitoring Recommendations
- Forward WordPress, PHP-FPM, and web server logs to a centralized SIEM for retention and correlation
- Enable WordPress audit logging to capture administrative actions following suspicious plugin requests
- Track outbound connections from web hosts and alert on connections to non-allowlisted destinations
How to Mitigate CVE-2026-27410
Immediate Actions Required
- Update the Slimstat Analytics plugin to version 5.4.0 or later on all affected WordPress sites
- Audit the site for unexpected administrative users, PHP files in uploads directories, and modified plugin or theme files
- Restrict access to wp-slimstat endpoints behind a web application firewall until the update is applied
Patch Information
Upgrade wp-slimstat to version 5.4.0 or later. The fixed release addresses the unsafe deserialization path. See the Patchstack vulnerability entry for vendor reference and version details.
Workarounds
- Disable and remove the Slimstat Analytics plugin until it can be updated to a patched version
- Deploy WAF rules that block requests containing PHP serialized object markers targeting wp-slimstat endpoints
- Restrict plugin endpoints to authenticated administrative IP ranges where feasible
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
