CVE-2026-28149 in Headless Single Sign On Plugin
Summary
by MITRE • 08/13/2026
Unauthenticated PHP Object Injection in Headless Single Sign On <= 1.6 versions.
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Analysis
by VulDB Data Team • 08/13/2026
This vulnerability represents a critical security flaw in the Headless Single Sign On plugin for WordPress systems, specifically affecting versions up to and including 1.6. The issue stems from improper input validation and sanitization within the plugin's handling of serialized PHP objects, creating an unauthenticated remote code execution vector that can be exploited by attackers without requiring any login credentials or administrative privileges. The vulnerability manifests when the application deserializes user-controllable data without adequate security measures, allowing malicious actors to inject crafted serialized objects that can execute arbitrary PHP code on the target server.
The technical implementation of this flaw involves the plugin's failure to properly validate and sanitize serialized data received through HTTP parameters or headers. When the system processes these objects during authentication flows or session management operations, it performs unserialize() operations on data that originates from external sources without sufficient security controls. This pattern directly aligns with CWE-502 which specifically addresses deserialization of untrusted data vulnerabilities. Attackers can leverage this weakness by crafting malicious serialized PHP objects that, when processed by the vulnerable plugin, trigger unintended code execution within the web application's context.
The operational impact of this vulnerability extends far beyond simple data theft or modification. An attacker with access to a vulnerable Headless Single Sign On installation can achieve full system compromise through remote code execution capabilities. This includes but is not limited to arbitrary file manipulation, database access, privilege escalation, and potential lateral movement within network environments where WordPress systems reside. The unauthenticated nature of the exploit means that attackers do not require any legitimate credentials to begin their attack operations, making this vulnerability particularly dangerous for publicly accessible web applications. The vulnerability can also be combined with other exploitation techniques to create more sophisticated attack chains.
Security professionals should immediately implement mitigation strategies including updating to patched versions of the Headless Single Sign On plugin, implementing web application firewalls with rules specifically targeting known malicious patterns, and conducting thorough security assessments of affected systems. Network segmentation and monitoring solutions should be deployed to detect unusual activity patterns that may indicate exploitation attempts. The ATT&CK framework categorizes this vulnerability under T1203 - Exploitation for Client Execution, indicating that attackers can leverage such flaws to execute arbitrary code on target systems. Additionally, organizations should consider implementing principle of least privilege access controls and regularly auditing plugin installations to ensure only necessary components remain active on production systems. The vulnerability also highlights the importance of secure coding practices around object serialization and deserialization processes within web applications, emphasizing the need for proper input validation and sanitization techniques that align with industry best practices established by organizations such as OWASP and NIST.