CVE-2026-63228 in Koollab LMS
Summary
by MITRE • 07/29/2026
An unrestricted image upload vulnerability in Koollab LMS allowed an authenticated attacker to upload malicious content disguised as an image file via the feedback mail registration endpoint, potentially enabling further attacks on the server.
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Analysis
by VulDB Data Team • 07/29/2026
The vulnerability identified in Koollab LMS represents a critical security flaw that undermines the integrity of the learning management system's file upload mechanisms. This unrestricted image upload vulnerability specifically targets the feedback mail registration endpoint, which serves as an entry point for authenticated users to submit content. The flaw stems from insufficient validation and sanitization processes that fail to properly verify the actual content of uploaded files, allowing attackers to bypass security controls by disguising malicious payloads within what appears to be legitimate image files. The vulnerability operates under the broader category of insecure file handling practices that have been documented in numerous security frameworks including CWE-434 which specifically addresses unrestricted upload of file with dangerous type.
The technical implementation of this flaw enables an authenticated attacker to execute a sophisticated social engineering attack by leveraging the system's trust in standard image file formats. When users submit feedback through the registration endpoint, the system accepts files based on their extension rather than their actual content, permitting the upload of malicious code disguised as image files such as jpg, png, or gif extensions. This misconfiguration creates a pathway for attackers to potentially execute arbitrary code on the server, gain unauthorized access to sensitive data, or establish persistent backdoors within the LMS infrastructure. The attack vector aligns with common tactics described in the MITRE ATT&CK framework under the T1566 technique for "Phishing with Malicious Attachments" and T1078 for "Valid Accounts" as the attacker requires authentication to exploit this vulnerability.
The operational impact of this vulnerability extends beyond simple data compromise, potentially enabling attackers to escalate privileges and move laterally within the network infrastructure. Once a malicious file is successfully uploaded and executed, the attacker could leverage the compromised LMS system as a foothold for broader attacks against other systems within the organization's network. The vulnerability's persistence potential means that even after initial exploitation, the malicious code could continue to operate undetected, providing ongoing access to sensitive educational data including student records, course materials, and administrative information. This risk is particularly concerning in educational environments where LMS systems often contain vast amounts of personally identifiable information and intellectual property.
Effective mitigation strategies must address both immediate remediation and long-term security architecture improvements. Organizations should implement strict file type validation using content-based verification rather than relying solely on file extensions, ensuring that uploaded files are inspected for actual content characteristics that match their claimed types. The system should employ robust sanitization processes including MIME type checking, file signature verification, and the implementation of secure file storage mechanisms that prevent execution of uploaded content. Additionally, network segmentation and access controls should be strengthened to limit potential lateral movement if exploitation occurs. Security monitoring should include detection of unusual upload patterns and automated scanning of all uploaded files for known malicious signatures or suspicious behaviors. The remediation process should also incorporate regular security assessments and penetration testing to identify similar vulnerabilities across the entire system architecture.