CVE-2022-35649 in Moodle
Summary
by MITRE • 07/25/2022
The vulnerability was found in Moodle, occurs due to improper input validation when parsing PostScript code. An omitted execution parameter results in a remote code execution risk for sites running GhostScript versions older than 9.50. Successful exploitation of this vulnerability may result in complete compromise of vulnerable system.
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Analysis
by VulDB Data Team • 08/27/2022
The vulnerability identified as CVE-2022-35649 represents a critical security flaw within the Moodle learning management system that stems from inadequate input validation during PostScript code processing. This weakness specifically manifests when Moodle handles file uploads or content processing that involves PostScript format interpretation, creating an avenue for malicious actors to exploit the system through remote code execution. The vulnerability is particularly concerning because it leverages the GhostScript library, which serves as a critical component for rendering PostScript and PDF documents within the platform. When Moodle processes user-supplied PostScript content without proper sanitization, it fails to adequately validate the input parameters, allowing attackers to inject malicious code that can be executed within the system context.
The technical exploitation of this vulnerability occurs through a specific parameter omission within the GhostScript execution chain, where the system fails to properly validate or sanitize the input parameters passed to the GhostScript interpreter. This flaw falls under CWE-20, which describes improper input validation, and specifically relates to CWE-78, which addresses OS command injection, as the vulnerable system can be coerced into executing arbitrary commands through the PostScript processing pipeline. The attack vector requires an authenticated user with sufficient privileges to upload or process PostScript content, though in some configurations the vulnerability may be exploitable by unauthenticated attackers. The exploitation process typically involves crafting malicious PostScript code that includes shell command execution directives, which then get processed by the vulnerable GhostScript version. This vulnerability is particularly dangerous because it allows attackers to execute commands with the privileges of the web server process, potentially leading to complete system compromise.
The operational impact of CVE-2022-35649 extends far beyond simple data theft or service disruption, as successful exploitation can result in full system compromise and persistent backdoor access. Attackers who successfully exploit this vulnerability can gain administrative control over Moodle installations, potentially leading to data exfiltration, system modification, or use of the compromised system as a launchpad for further attacks within the network. The risk is amplified by the fact that many organizations may be running outdated GhostScript versions that lack the security patches available in GhostScript 9.50 and later. This vulnerability affects organizations that rely heavily on document processing capabilities within Moodle, particularly those that allow users to upload various document formats including PostScript files. The impact is especially severe for educational institutions and training organizations that may have extensive Moodle deployments with multiple users and complex configurations.
Organizations should prioritize immediate remediation of this vulnerability by upgrading to GhostScript version 9.50 or later, which includes proper input validation and parameter handling that prevents the exploitation scenario. Additionally, implementing network segmentation and access controls can help limit the potential impact if exploitation occurs, while also monitoring for unusual file upload patterns or execution activities. The mitigation strategy should include disabling unnecessary document processing features where possible and implementing strict input validation at multiple layers of the application architecture. Security teams should also consider implementing web application firewalls and intrusion detection systems that can identify and block suspicious PostScript processing patterns. According to the ATT&CK framework, this vulnerability maps to technique T1059.007 for command and script interpreter, specifically the use of PowerShell and command-line interfaces, as attackers can leverage this vulnerability to execute arbitrary commands on the compromised system. Regular security assessments and vulnerability scanning should be implemented to identify other potential entry points, while also ensuring that all third-party components and libraries are kept current with security patches to prevent similar vulnerabilities from emerging in the future.