CVE-2026-19224 in Hummingbird Performance Plugin
Summary
by MITRE • 09/04/2026
The Hummingbird Performance WordPress plugin before 3.21.2 does not restrict a network-wide setting to network administrators, allowing an administrator of any single site on a multisite network to execute arbitrary code across the entire network.
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Analysis
by VulDB Data Team • 09/04/2026
The vulnerability identified in versions of the Hummingbird Performance WordPress plugin prior to version 3.21.2 represents a critical failure in access control logic within multi-site environments. This flaw stems from an insufficient restriction on administrative privileges, specifically regarding how certain configuration settings are propagated and enforced across a WordPress multisite network. In a standard single-site installation, this issue would be less severe as it primarily affects the local administrator of that specific site. However, in a multisite architecture where multiple distinct websites operate under a single WordPress installation sharing a common database and codebase, the implications are significantly more profound due to the elevated trust model typically assigned to network administrators versus individual site administrators.
The core technical flaw lies in the plugin's handling of global performance settings that have side effects capable of executing arbitrary code or altering system behavior across all sites within the network. The software fails to verify whether the user initiating a change possesses Network Administrator privileges, which are required for actions with cross-site impact. Instead, it accepts and processes these requests from users holding only Site Administrator roles on individual sub-sites. This misconfiguration allows any authenticated administrator of any single site in the network to modify settings that affect the entire infrastructure without proper authorization checks. The vulnerability essentially bypasses the intended hierarchical security model where global changes are reserved for high-privilege accounts, thereby creating a path for privilege escalation from a low-level site admin role to full control over the multisite environment.
From an operational perspective, this weakness enables an attacker who has compromised or been granted access as a regular site administrator to execute arbitrary code across the entire network. By manipulating these unrestricted settings, such an actor can inject malicious scripts, alter server configurations, or exploit other vulnerabilities present in shared plugins and themes used by all sites on the network. The impact is not limited to data theft but extends to complete compromise of the underlying infrastructure serving multiple distinct entities. This could lead to widespread defacement, distribution of malware to visitors across various domains, and potential exfiltration of sensitive data stored within any of the connected websites. The ability to execute code globally amplifies the blast radius significantly compared to isolated site compromises.
This vulnerability aligns with CWE-269, which describes Improper Privilege Management, as it involves a failure to enforce proper authorization levels for administrative functions. Furthermore, in the context of the MITRE ATT&CK framework, this behavior is indicative of techniques related to Lateral Movement and Defense Evasion, where an attacker uses compromised credentials on one node to gain access to other parts of the network that were previously out of reach due to stricter security controls. The exploitation relies on the assumption that site administrators are trusted with global configurations, a false premise in secure multisite deployments.
To mitigate this risk, organizations running WordPress multisites must immediately upgrade the Hummingbird Performance plugin to version 3.21.2 or later, where these access control checks have been corrected to enforce network-wide administrative privileges for such settings. Until an update is applied, administrators should review user roles within their multisite installation and restrict site administrator capabilities wherever possible, adhering to the principle of least privilege. Additionally, implementing strict input validation on all configuration endpoints that affect global state can provide a layer of defense against similar logic flaws in other plugins. Regular auditing of plugin permissions and keeping software up to date are essential practices for maintaining security integrity in complex WordPress environments.