CVE-2026-102580 in Moodle
Summary
by MITRE • 09/30/2026
A flaw was found in Moodle. An authenticated attacker can supply an improperly validated audience class name to the Report Builder component, allowing arbitrary class instantiation. This vulnerability enables the unauthorized creation of internal program objects, which may result in unexpected application behavior.
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Analysis
by VulDB Data Team • 09/30/2026
The identified vulnerability resides within the Report Builder module of the Moodle learning management system and represents a critical failure in input validation mechanisms for authenticated users. Specifically, the flaw allows an attacker who has valid credentials to supply an improperly validated audience class name as part of their request payload. This lack of rigorous sanitization or allow-listing enables arbitrary class instantiation, a technique often referred to as insecure deserialization or unsafe reflection depending on the underlying implementation details. By manipulating this parameter, the attacker bypasses standard security controls that are designed to restrict object creation to predefined, safe classes within the application's architecture.
From a technical perspective, this vulnerability exploits the dynamic nature of PHP class loading mechanisms in Moodle. When an audience class name is provided without sufficient verification against a whitelist of permitted classes, the system attempts to instantiate the specified class directly from memory or file storage. This process bypasses standard initialization checks and security boundaries inherent to the application's design. The ability to create arbitrary internal program objects means that the attacker can potentially trigger side effects associated with those objects' constructors or methods. These side effects may include database queries, file system operations, or execution of other backend logic that was not intended for public access via this specific interface.
The operational impact of this vulnerability is significant due to its potential to lead to unexpected application behavior and further exploitation vectors. While the immediate description highlights unauthorized object creation, such flaws are frequently precursors to more severe outcomes like Remote Code Execution or privilege escalation if the instantiated classes interact with sensitive system resources. For instance, certain internal Moodle objects might have access to configuration data, user session information, or administrative functions that are otherwise restricted. An authenticated attacker could leverage this instability to disrupt service availability through resource exhaustion or cause data integrity issues by manipulating backend states in unintended ways. The risk is particularly acute because it requires only authentication, a barrier that many users and institutions assume provides sufficient security perimeter protection.
This vulnerability aligns with CWE-20 Improper Input Validation and CWE-470 Use of Externally-Controlled Input to Select Classes or Code, as the system fails to restrict input to expected values before processing it into executable logic. In terms of offensive cybersecurity frameworks, this behavior is consistent with ATT&CK technique T1559 Inter-Process Communication, where an attacker manipulates internal application components to achieve unauthorized actions. It also touches upon aspects of T1078 Valid Accounts, as the exploitation relies on legitimate user credentials to bypass initial access controls and reach the vulnerable component within the Report Builder module.
Mitigation strategies must focus on strict input validation and defense-in-depth principles. The primary remediation involves implementing a rigorous allow-list mechanism for audience class names in the Report Builder codebase, ensuring that only explicitly approved classes can be instantiated by user-supplied inputs. Developers should avoid using dynamic instantiation based directly on untrusted data without extensive verification. Additionally, applying principle of least privilege to database accounts and file system permissions used by Moodle can limit the blast radius if an object is successfully instantiated with malicious intent. Organizations running affected versions of Moodle should apply vendor-provided security patches immediately upon release. Until patching is possible, restricting access to the Report Builder module to only those users who absolutely require it can reduce the attack surface available to potential adversaries exploiting this flaw.