Fleet has SAML authentication vulnerability due to improper SAML response validation
Date: 2025-03
Affected: go/github.com/fleetdm/fleet/v4, go/github.com/fleetdm/fleet/v4, go/github.com/fleetdm/fleet/v4
Attack vector: deepfake
Category: vulnerability-disclosure
Severity: Critical
CVE: CVE-2025-27509
CWE: CWE-285
CWE-74

### Summary A vulnerability in Fleet’s SAML authentication handling could allow an attacker to forge authentication assertions and gain unauthorized access to Fleet. In certain configurations, this could result in the creation of new user accounts, including administrative accounts. This issue affects Fleet deployments using single sign-on (SSO). ### Impact In vulnerable versions of Fleet, an attacker could craft a specially-formed SAML response to: - Forge authentication assertions, potentially impersonating legitimate users. - If Just-In-Time (JIT) provisioning is enabled, the attacker could provision a new administrative user account. - If MDM enrollment is enabled, certain endpoints could be used to create new accounts tied to forged assertions. This could allow unauthorized access to Fleet, including administrative access, visibility into device data, and modification of configuration. ### Patches This issue is addressed in commit [fc96cc4](https://github.com/fleetdm/fleet/commit/fc96cc4e91047250afb12f65ad70e90b30a7fb1c) and is available in Fleet version 4.64.2. The following backport versions also address this issue: - 4.63.2 - 4.62.4 - 4.58.1 - 4.53.2 ### Workarounds If an immediate upgrade is not possible, Fleet users should temporarily disable [single-sign-on (SSO)](https://fleetdm.com/docs/deploy/single-sign-on-sso) and use password authentication. ### Credit Thank you @hakivvi, as well as Jeffrey Hofmann and Colby Morgan from the Robinhood Red Team f


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