CVE-2022-21663 in WordPress
Summary
by MITRE • 01/07/2022
WordPress is a free and open-source content management system written in PHP and paired with a MariaDB database. On a multisite, users with Super Admin role can bypass explicit/additional hardening under certain conditions through object injection. This has been patched in WordPress version 5.8.3. Older affected versions are also fixed via security release, that go back till 3.7.37. We strongly recommend that you keep auto-updates enabled. There are no known workarounds for this issue.
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Analysis
by VulDB Data Team • 01/09/2022
This vulnerability represents a critical object injection flaw in WordPress multisite installations that allows users with Super Admin privileges to bypass security hardening measures through improper input validation. The issue specifically affects WordPress versions prior to 5.8.3 and includes older releases down to 3.7.37, indicating a long-standing security gap that has persisted across multiple major versions. The vulnerability stems from insufficient sanitization of user inputs when processing object serialization and deserialization operations within the multisite administration framework, creating an attack surface where maliciously crafted data can manipulate object states and bypass intended access controls.
The technical implementation of this vulnerability involves the exploitation of improper object handling within WordPress's multisite administrative functions where Super Admin users can leverage crafted input to inject malicious objects into the system. This type of vulnerability maps directly to CWE-502 which defines insecure deserialization as a critical weakness in software applications. The attack vector specifically targets the serialization mechanisms used by WordPress to store and retrieve complex data structures, particularly in multisite configurations where administrative privileges are more expansive. When combined with the Super Admin role, this creates a privilege escalation pathway that allows attackers to manipulate system objects in ways that should normally be restricted.
The operational impact of this vulnerability extends beyond simple privilege escalation as it undermines the fundamental security model of WordPress multisite installations. Super Admin users can potentially bypass additional security measures that have been explicitly implemented by site administrators, including custom access controls, network-level restrictions, and other hardening measures that are designed to protect against unauthorized access. This creates a scenario where a compromised Super Admin account could be leveraged to circumvent even sophisticated security configurations that were put in place specifically to protect against such attacks. The vulnerability affects the integrity of the entire multisite administrative framework and can lead to complete system compromise if not addressed promptly.
Mitigation strategies for this vulnerability require immediate implementation of the patched WordPress versions, with version 5.8.3 being the primary recommended update. Organizations should ensure that all affected installations are updated to the latest security releases, with particular attention to legacy systems that may not have received automatic updates. The security release for older versions demonstrates that this vulnerability was recognized as high-risk and required immediate attention across multiple WordPress version streams. System administrators should enable auto-updates to prevent future exposure to similar vulnerabilities, as the lack of workarounds means that manual mitigation is not possible. This vulnerability also highlights the importance of proper input validation and secure object handling practices that align with ATT&CK framework techniques related to privilege escalation and defense evasion. Organizations should conduct comprehensive security audits of their multisite installations to ensure that no other similar vulnerabilities exist in their WordPress deployments.