Improper validation of SAML responses

Vulnerability

Apache Guacamole versions 1.2.0 and 1.3.0 do not properly validate responses received from a SAML identity provider. This vulnerability resides in the SAML authentication module. If SAML support is enabled, the lack of proper validation allows an attacker to manipulate SAML responses. The affected versions are explicitly 1.2.0 and 1.3.0 [1].

Exploitation

An attacker must have network access to the Guacamole server and the ability to intercept or craft SAML responses. The attacker can send a malicious SAML response that claims the identity of another user. No authentication is required beyond the ability to interact with the SAML authentication flow. The attacker does not need prior access to the target user's account [1].

Impact

Successful exploitation allows the attacker to assume the identity of any other Guacamole user. This leads to unauthorized access to the victim's Guacamole session, potentially including remote desktop connections and other resources accessible through Guacamole. The impact is high confidentiality and integrity compromise, as the attacker can perform actions as the impersonated user [1].

Mitigation

The issue is fixed in Apache Guacamole 1.4.0, released on January 11, 2022 [1]. Users should upgrade to version 1.4.0 or later. If upgrading is not immediately possible, disabling SAML authentication is a workaround. No other workarounds are mentioned in the reference [1].