LORIS is a self-hosted web application used for neuroimaging research data and project management. In affected versions, a logic error in the FilesDownloadHandler component permits directory traversal or similar unauthorized access, enabling external parties to access files or directories outside the intended download scope. This is classified under CWE-552, which concerns files or directories accessible to external parties due to improper access control. The vulnerability has a CVSS 3.1 base score of 7.7, indicating high severity, with network attack vector, low attack complexity, requiring low privileges but no user interaction, and impacts confidentiality with a scope change. The issue is resolved in LORIS versions 27.0.3 and 28.0.1.

An attacker with low privileges can exploit this vulnerability remotely over the network without user interaction to access sensitive files or directories outside the intended download directories. This results in a confidentiality breach but does not affect integrity or availability. The scope of the impact is changed, meaning the vulnerability affects resources beyond the initially intended security boundary.

A fix is available in LORIS versions 27.0.3 and 28.0.1. Users should upgrade to one of these versions or later to remediate this vulnerability. Since this is a self-hosted application, administrators must apply the update themselves. Patch status is confirmed by the vendor's versioning information. No additional mitigation guidance is provided or required beyond applying the official fix.