Executive brief
Open WebUI is an interface for interacting with large language models. A vulnerability in its LDAP authentication module allows attackers to log into any user account, including administrator accounts, by providing a valid username and an empty password. This could lead to full account takeover, unauthorized access to private chats, and exposure of sensitive API keys or configuration data.
Technical details
The LDAP authentication endpoint in Open WebUI fails to validate that the submitted password is non-empty before attempting a Simple Bind against the LDAP server. According to RFC 4513, a Simple Bind with a valid Distinguished Name (DN) and an empty password is treated as 'unauthenticated simple authentication,' which many LDAP servers (like OpenLDAP and some Active Directory configurations) treat as a successful bind. The LdapForm Pydantic model lacks a min_length constraint on the password field, allowing the empty string to reach the backend/open_webui/routers/auths.py logic. If the bind succeeds, the application issues a valid session token for the target user. This is exploitable if ENABLE_LDAP is true and the underlying LDAP server allows unauthenticated binds.
Affected products
- Open WebUI Open WebUI <= 0.8.12
Timeline
- 2026-05-05: disclosed: Vulnerability reported to GitHub Advisory Database
- 2026-05-08: advisory: GHSA-2r4p-jpmg-48f4 published
- 2026-05-08: patched: Fixed in version 0.9.0