CVE-2026-25138: Rucio WebUI has Username Enumeration via Login Error Message
Summary The WebUI login endpoint returns distinct error messages depending on whether a supplied username exists, allowing unauthenticated attackers to enumerate valid usernames.
Details When submitting invalid credentials to /ui/login, the WebUI responds with different error messages based on the existence of the provided username (identity). A non-existent username results in an error indicating that no account is associated with the identity, while an existing username with an incorrect password produces a different authentication-related error.
This behavioral difference allows an attacker to distinguish valid usernames from invalid ones by observing the response content.
Proof of Concept Bogus Login (Non-existent Username "15251087") Response contains: Cannot get find any account associated with 15251087 identity.
Bogus Login (Existing Username "root", Wrong Password) Response contains: Cannot get auth token. It is possible that the presented identity root is not mapped to any Rucio account root.
The difference in error messages confirms whether a username exists.
Impact An unauthenticated attacker can enumerate valid usernames, which may be leveraged for targeted password guessing, credential stuffing, or social engineering attacks.
Remediation / Mitigation Return a generic authentication failure message for all login errors, regardless of whether the username exists. Avoid disclosing account or identity existence through error responses. Consider implementing rate limiting or additional login throttling to further reduce abuse.
Reources: - OWASP Authentication Cheat Sheet - Authentication and Error Messages: https://cheatsheetseries.owasp.org/cheatsheets/AuthenticationCheatSheet.html#authentication-and-error-messages
Other sources
Rucio is a software framework that provides functionality to organize, manage, and access large volumes of scientific data using customizable policies. Prior to versions 35.8.3, 38.5.4, and 39.3.1, the WebUI login endpoint returns distinct error messages depending on whether a supplied username exists, allowing unauthenticated attackers to enumerate valid usernames. Versions 35.8.3, 38.5.4, and 39.3.1 fix the issue.
— NVD
Affected Software
Event History
Frequently Asked Questions
What is the severity of CVE-2026-25138?
CVE-2026-25138 is categorized as a medium severity vulnerability due to its potential for username enumeration.
How do I fix CVE-2026-25138?
To fix CVE-2026-25138, upgrade rucio-webui to the latest version 39.3.1, 38.5.4, or 35.8.3, as applicable.
What are the implications of CVE-2026-25138?
The implications of CVE-2026-25138 include the risk of unauthorized username enumeration, which can facilitate further attacks.
Which versions of rucio-webui are affected by CVE-2026-25138?
CVE-2026-25138 affects rucio-webui versions between 39.0.0rc1 and 39.3.1, between 36.0.0rc1 and 38.5.4, and all versions up to 35.8.3.
Is authentication compromised by CVE-2026-25138?
While CVE-2026-25138 does not compromise authentication directly, it enables attackers to gather valid usernames, increasing the risk of account compromise.