SAML Vulnerability in Logto Affecting Open-Source Authentication Infrastructure

CVE-2026-55789

What is CVE-2026-55789?

Logto, the modern open-source authentication infrastructure for SaaS and AI applications, experienced a significant vulnerability prior to version 1.41.0. This issue arose within its self-hosted SAML application identity provider (IdP), where user-controlled profile attributes were improperly integrated into a SAML XML template. Specifically, attributes like name and email could be exploited by an authenticated low-privilege user to inject arbitrary XML markup. This manipulation could lead to the signing of forged SAML attributes, potentially allowing unauthorized privilege escalation at relying service providers that utilize SAML attributes for authorization. The vulnerability has been addressed in Logto version 1.41.0.

References