CVE-2020-25629 in Moodle
Summary
by MITRE • 12/08/2020
A vulnerability was found in Moodle where users with "Log in as" capability in a course context (typically, course managers) may gain access to some site administration capabilities by "logging in as" a System manager. This affects 3.9 to 3.9.1, 3.8 to 3.8.4, 3.7 to 3.7.7, 3.5 to 3.5.13 and earlier unsupported versions. This is fixed in 3.9.2, 3.8.5, 3.7.8 and 3.5.14.
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Analysis
by VulDB Data Team • 12/13/2020
This vulnerability in Moodle represents a critical privilege escalation flaw that undermines the platform's security model by allowing unauthorized users to access administrative functions through a seemingly benign feature. The issue specifically affects the "Log in as" capability within course contexts, which is typically granted to course managers and other trusted users. When exploited, this vulnerability enables attackers to bypass normal access controls and gain access to system-level administrative functions that should be restricted to users with explicit system-wide privileges.
The technical flaw stems from improper privilege validation within Moodle's authentication and authorization mechanisms. When a user with course-level "Log in as" capability attempts to impersonate a system manager, the platform fails to properly enforce the distinction between course-level and system-level privileges. This creates a path where course managers can access administrative functions that are normally restricted to users with direct system administrator permissions. The vulnerability exists because the system does not adequately verify that the target user being impersonated possesses the necessary system-level privileges required for the administrative functions being accessed.
The operational impact of this vulnerability is severe as it allows attackers to escalate their privileges from course-level access to full system administration capabilities. This means that an attacker who gains access to a course manager account can potentially access sensitive system configurations, user management functions, course data manipulation, and other administrative features that could lead to complete system compromise. The vulnerability affects multiple major versions of Moodle, indicating it was a widespread issue that required coordinated patching across different release lines. The fact that it impacted versions from 3.5 through 3.9 demonstrates the longevity and significance of the flaw in the platform's security architecture.
The vulnerability aligns with CWE-285, which addresses improper authorization issues in software systems, and represents a classic case of privilege escalation through insufficient access control validation. From an ATT&CK framework perspective, this vulnerability maps to privilege escalation techniques where adversaries leverage existing access to elevate their privileges within a system. The attack vector specifically involves the use of legitimate administrative features that are misconfigured or improperly validated, making it particularly dangerous as it can be exploited through normal system usage patterns. Organizations using affected Moodle versions should immediately implement the security patches released in versions 3.9.2, 3.8.5, 3.7.8, and 3.5.14, while also monitoring for suspicious login patterns and ensuring proper user privilege assignments to minimize the impact of potential exploitation.