LiteLLM’s authentication logic allows an attacker who possesses a token from the configured identity provider to log in as any existing user. The vulnerability arises because the system performs an email-based fallback lookup without verifying the email_verified claim. An attacker can forge a token containing an unverified email address that matches a victim’s account, thereby inheriting the victim’s role, including proxy_admin privileges. Once authenticated, the attacker can irrevocably overwrite the victim’s stored identity binding, granting permanent unauthorized access to administrative endpoints that expose API keys and user management facilities.

The affected product is BerriAI LiteLLM. Specific version information is not supplied, so any deployment of LiteLLM that relies on the default JWT authentication configuration is potentially vulnerable.

The CVSS score of 7.6 indicates high severity, and the EPSS score of less than 1% suggests a low but present likelihood of exploitation. The vulnerability is not listed in the CISA KEV catalog. Based on the description, it is inferred that an attacker must first acquire a valid JWT from the identity provider; this could be achieved through credential compromise or social engineering. Given that the attack exploits an email-based fallback lookup, the attacker only needs to know or guess a victim’s email address. Once the forged token is presented, the authentication bypass occurs immediately, allowing the attacker to impersonate the victim, elevate privileges, and create a persistent attack vector by overwriting the victim’s identity binding.