GHSA-86cx-wwf4-phq4

Summary

An authorization bypass vulnerability exists in the file sharing mechanism of Openlist. Due to a flawed, non-separator-aware path validation check, an authenticated user can create share links for files outside their restricted base directory. This allows an attacker to bypass tenant/user isolation and gain unauthorized read access to arbitrary files within the system.

Details

When a user attempts to create or update a file share, the application must verify that the requested file path falls within the user's assigned BasePath. However, in server/handles/sharing.go, this authorization check relies on a simple string prefix function: strings.HasPrefix(requested_path, user.BasePath).

Because strings.HasPrefix does not account for directory separators (e.g., /), an attacker whose BasePath is assigned to /base can supply a target path like /base2/secret_document.txt. The validation strings.HasPrefix("/base2/secret_document.txt", "/base") evaluates to true, successfully passing the authorization filter.

Once the share is created, the public share download/list handlers unwrap and serve the file based on the stored absolute path without re-verifying the creator's current directory scope, granting the attacker horizontal access to unauthorized data.

PoC

Prerequisites:

1. A system with at least two distinct directories at the root level: /base and /base2.
2. A sensitive file exists at /base2/secret.txt.
3. An attacker account with the CanShare permission enabled and its Base path strictly limited to /base.

Exploitation Steps:

1. Log in as the attacker account and obtain the JWT authorization token.
2. Send a POST request to create a new share, intentionally targeting the unauthorized sibling directory /base2:

POST /api/share/create HTTP/1.1
Host: <your-openlist-host>
Authorization: <attacker-jwt-token>
Content-Type: application/json

{
  "files": ["/base2/secret.txt"],
  "pwd": "",...