CVE-2026-54091 in File Browser
Summary
by MITRE • 06/25/2026
File Browser is a file managing interface for uploading, deleting, previewing, renaming, and editing files within a specified directory. Prior to 2.63.6, File Browser's public share handlers rebase the share owner's filesystem root to the shared directory and then evaluate descendant paths against the owner's global and per-user rules using the rebased relative path instead of the original path relative to the owner's scope. As a result, an attacker who knows a public directory share URL can access files and subdirectories that the owner explicitly blocked with rules, as long as those blocked paths are located underneath the shared directory. In the simplest case this is an unauthenticated information disclosure through `GET /api/public/share/*` and `GET /api/public/dl/*`. This vulnerability is fixed in 2.63.6.
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Analysis
by VulDB Data Team • 06/26/2026
The File Browser vulnerability represents a critical access control flaw that undermines the security model of the application's public sharing functionality. This issue affects versions prior to 2.63.6 and stems from improper path validation during public share operations. The vulnerability manifests when the system incorrectly processes file paths by rebasing the share owner's filesystem root to the shared directory, subsequently evaluating descendant paths against access rules using the rebased relative path rather than maintaining the original path context relative to the owner's scope. This fundamental flaw creates a path traversal condition that allows unauthorized access to files and directories that should remain protected.
The technical implementation of this vulnerability exploits the inconsistency between how public shares handle path evaluation and how access control rules are enforced. When a user creates a public share, the system should maintain strict contextual boundaries between the shared directory and the underlying filesystem structure. However, the flawed implementation causes the system to incorrectly interpret access control rules by applying them to a rebased path rather than the original absolute path context. This misalignment allows an attacker who possesses knowledge of a public directory share URL to bypass explicit blocking rules that were designed to prevent access to sensitive files or subdirectories located beneath the shared directory.
The operational impact of this vulnerability extends beyond simple information disclosure, creating potential pathways for unauthorized data access and exfiltration. Attackers can leverage this flaw through unauthenticated requests to the API endpoints `GET /api/public/share/` and `GET /api/public/dl/`, effectively circumventing the intended access controls that prevent access to files and directories the share owner explicitly blocked. This vulnerability specifically targets the public sharing feature, which is designed to provide controlled access to specific directories while maintaining security boundaries for the remainder of the filesystem. The implications are particularly severe because it allows attackers to discover and access files that should remain hidden even within a publicly shared directory structure.
This vulnerability aligns with CWE-22 (Improper Limitation of a Pathname to a Restricted Directory) and CWE-23 (Relative Path Traversal), both of which address path manipulation flaws in file system access control. The issue also maps to ATT&CK technique T1078 (Valid Accounts) and T1566 (Phishing) as attackers can leverage this vulnerability to gain unauthorized access to sensitive data without requiring authentication or social engineering. The lack of proper path validation creates a persistent security weakness that undermines the principle of least privilege enforcement within the application's access control system.
The mitigation strategy involves updating to File Browser version 2.63.6, which implements corrected path evaluation logic that properly maintains the original path context when applying access control rules. Organizations should also conduct immediate reviews of existing public shares to identify any potential unauthorized access that may have occurred prior to the patch deployment. System administrators should implement additional monitoring for API endpoints related to public sharing and establish alerting mechanisms for unusual access patterns. The fix ensures that access control rules are properly enforced against the original path context rather than a rebased relative path, restoring proper security boundaries within the application's sharing functionality.