CVE-2026-78533 in Qwery Plugin
Summary
by MITRE • 10/10/2026
Unauthenticated PHP Object Injection in Qwery <= 3.6.1 versions.
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Analysis
by VulDB Data Team • 10/10/2026
The vulnerability identified as an unauthenticated PHP object injection flaw within Qwery versions up to and including 3.6.1 represents a critical security deficiency that allows attackers to execute arbitrary code on the target server without requiring valid credentials. This type of vulnerability stems from the application's improper handling of user-supplied input during the deserialization process, specifically when processing data intended for PHP object instantiation. In modern web applications utilizing frameworks or libraries that rely heavily on serialization for state management, caching, or session storage, the integrity of this mechanism is paramount. When an application accepts external data and passes it directly to a function such as unserialize without rigorous validation against a whitelist of expected classes, it creates an attack vector where malicious actors can manipulate the serialized payload to instantiate arbitrary objects with controlled properties.
The technical root cause lies in the lack of input sanitization and type checking before deserialization occurs. PHP's object injection vulnerabilities are often exploited through gadget chains, which are sequences of existing application methods that can be chained together to achieve a specific outcome, such as remote code execution or denial of service. By crafting a malicious serialized string containing references to classes available within the Qwery environment or its dependencies, an attacker can trigger these unintended side effects. Since this vulnerability is unauthenticated, it significantly lowers the barrier for exploitation, allowing any network-accessible user with basic scripting knowledge to interact with the vulnerable endpoint and inject payloads directly into the application's memory space. This aligns closely with Common Weakness Enumeration identifier CWE-502, which describes deserialization of untrusted data as a distinct category of weakness that leads to severe security compromises.
The operational impact of this vulnerability is profound, potentially leading to complete system compromise. An attacker leveraging PHP object injection can achieve remote code execution by invoking methods like eval or file_get_contents with malicious arguments derived from the injected objects. This capability enables the exfiltration of sensitive data stored within the application's database or filesystem, modification of critical configuration files, and further pivoting into internal network segments if the server is part of a larger infrastructure. Furthermore, depending on the specific gadget chain utilized, it may also result in denial of service conditions by exhausting system resources through infinite loops or memory leaks triggered during object manipulation. The absence of authentication requirements means that automated scanning tools can rapidly identify and exploit this flaw across large numbers of instances, increasing the risk of widespread compromise.
To mitigate this vulnerability, immediate action is required to update Qwery to a version greater than 3.6.1 where the deserialization logic has been patched with proper input validation mechanisms. If an upgrade is not immediately feasible, administrators should implement strict allowlists for classes that are permitted during deserialization processes rather than relying on blacklist approaches which can be bypassed by discovering alternative gadget chains. Additionally, enabling PHP's built-in serialization handlers or using JSON instead of native PHP serialize functions where possible can reduce the attack surface significantly. From a defense-in-depth perspective, deploying web application firewalls with rulesets capable of detecting anomalous serialized payloads and restricting outbound network connections from the server to limit lateral movement are recommended supplementary controls. This incident underscores the importance of adhering to secure coding practices regarding data handling and aligns with ATT&CK technique T1059 which covers command and script interpretation, highlighting how initial access via injection can lead to broader system control.