CVE-2006-6017 in WordPress
Summary
by MITRE
WordPress before 2.0.5 does not properly store a profile containing a string representation of a serialized object, which allows remote authenticated users to cause a denial of service (application crash) via a string that represents a (1) malformed or (2) large serialized object, because the object triggers automatic unserialization for display.
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Analysis
by VulDB Data Team • 04/28/2026
WordPress versions prior to 2.0.5 contained a critical vulnerability in their user profile handling mechanism that could be exploited to cause denial of service conditions. The flaw existed in how the system processed serialized object data within user profiles, specifically when these objects were stored and subsequently displayed. This vulnerability was particularly dangerous because it leveraged the automatic unserialization process that occurs when serialized data is rendered for display purposes. The vulnerability was classified under CWE-127 as a "Sensitive Data Exposure" and also related to CWE-400 as "Uncontrolled Resource Consumption" due to the potential for resource exhaustion through malicious serialized data manipulation.
The technical implementation of this vulnerability stemmed from WordPress's handling of serialized PHP objects within user profile fields. When a user profile contained a serialized object string, the system would automatically attempt to unserialize this data for display purposes. Attackers could craft malicious serialized objects that either contained malformed data structures or excessively large data payloads. These crafted objects would trigger PHP's automatic unserialization process when the profile information was accessed, leading to application instability and potential crashes. The vulnerability was particularly insidious because it required authentication, meaning only legitimate users could exploit it, though this did not mitigate the severity of the impact.
The operational impact of this vulnerability extended beyond simple service disruption to potentially compromise the entire WordPress installation. When exploited, the malformed serialized objects could cause PHP processes to consume excessive memory resources or trigger fatal errors that would crash the application. This created a denial of service condition that could affect all users of the platform, particularly in multi-user environments where administrators might be targeted. The vulnerability could also serve as a stepping stone for more sophisticated attacks, as the application instability might create opportunities for privilege escalation or data corruption. From an attack framework perspective, this vulnerability aligned with ATT&CK technique T1499.004 for "Endpoint Denial of Service" and could be categorized under T1566.001 for "Phishing" if used to craft malicious profile data that would trigger the vulnerability upon display.
Mitigation strategies for this vulnerability required immediate patching of WordPress installations to version 2.0.5 or later, where the serialization handling was properly secured. Administrators should implement input validation and sanitization measures for all user profile data, particularly when dealing with serialized objects. The recommended approach included implementing strict validation of serialized data formats and limiting the size of serialized objects stored in profile fields. Additionally, monitoring systems should be deployed to detect unusual patterns in profile data that might indicate attempts to exploit this vulnerability. Organizations should also consider implementing web application firewalls to filter malicious serialized data before it reaches the application layer, and regular security audits should be conducted to identify and remediate similar serialization vulnerabilities in other components of the WordPress ecosystem.