CVE-2025-54875: 
NixOS vulnerability analysis and mitigation

CVE-2025-54875 affects FreshRSS, a free, self-hostable RSS aggregator, in versions 1.16.0 through 1.26.3. The vulnerability allows an unprivileged attacker to create a new admin user when registration is enabled through the exploitation of a hidden field 'newuseris_admin' that is typically used only in the user management admin page (GitHub Advisory). The vulnerability was discovered and reported by Inverle, and was fixed in version 1.27.0.

The vulnerability exists in the user creation functionality within FreshRSS/app/Controllers/userController.php. The code between lines 425-430 processes the 'newuseris_admin' parameter without performing proper access control checks. The vulnerability has been assigned a CVSS v3.1 score of 9.8 (Critical) with the vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H, indicating it can be exploited remotely with no privileges required and no user interaction (GitHub Advisory).

The vulnerability allows for full compromise of the FreshRSS instance, enabling attackers to access and alter user data. An attacker can create an administrative account without proper authorization, effectively gaining complete control over the system (GitHub Advisory).

The vulnerability has been fixed in FreshRSS version 1.27.0. Users are strongly advised to upgrade to this version to address the security issue. The fix was implemented through pull request #7783, which added proper access rights checks when creating new users (GitHub Release).